Lecture 4 - Exposure (continued) Video Lecture | Exposing Digital Photography by Harvard Extension School

hi everyone welcome to digital media e
10 I'm Dan I'm very excited about today
as I always am because we get to
continue working with exposure which is
of course a very fascinating interesting
topic we get to delve into some of the
related things that we really didn't get
a chance to talk about last week when we
were talking about the most fundamental
aspects of exposure but also I'm excited
because we we have some images that
we're going to show at the very end of
this class might recall a few weeks ago
that we were talking about as part of
the the critique and the precipitation
we're hoping that not only will you
submit your photos to critique on the
course blog but also you will show one
of your photos either in section or in
lecture hopefully you'll be there will
be an opportunity for you or there
should be there there has to be an
opportunity for you to do one or both
and so we're going to begin doing that
this week and if you haven't yet sort of
given that any thoughts if for some
reason we try to offer as many sections
as we could given the constraints of our
staff and their their schedules and also
with the the schedules of everyone who
submitted the surveys to us but if you
are unable to attend one of the sections
then do let us know even if you're at a
distance then do let us know we'll be
able to show one of your work in lecture
even though you're not able to be
physically present but speaking of at a
distance just as a reminder as always we
are on skype right now Expo digi photo
and that's the same for our sections
which by the way we have announced the
final section schedule that will persist
for the duration of the semester and it
is as follows it is for an in-person
section it's Wednesdays here in Harvard
Square at 5:30 p.m. Eastern led by
Shelley in 125 Mount Auburn Street all
this information can be found on the
course website and we have two online
sections one on Wednesdays at 6 p.m. and
another on Thursdays at 5:30 p.m.
please try to attend one of these
sections whether it's online or in
person
the Wednesday sections will cover
material from the previous week and the
Thursday one will cover for material for
that week so basically it's as you would
expect the section material will cover
what was last covered and/or what was
covered in their just previous lecture
basically it's a great way to not only
go over some questions or material that
you have questions on but also to show
off your own images get sort of a
critique on those in person and also get
to know some of your classmates that
will be very important for some of the
subsequent problem sets and projects
hopefully I'm not too subtle about that
particular hint but we'll talk about
that speaking of projects and problem
sets I do just want to do a quick
reminder for the due dates of some of
the items in particular project one is
due tonight so
in a few hours at 11:59 p.m. Eastern
Time it's now 7:45 p.m. Eastern time so
if you don't yet if you haven't
submitted yet hopefully you'll be able
to do that soon hopefully you already
have the images ready to go it's getting
a little late to just take the images
for the purposes of the project problem
set two is due this coming Wednesday at
the same time 11:59 p.m. and project two
was just released today as of a few
hours ago and we'll talk more about this
throughout the lecture but basically
this is one of the ones that I don't
really want don't want to overuse the
term excited but all the staff are
really excited because every year this
is the one that produces phenomenal
results everybody steps up and we're
hoping that you will as well and
basically the idea is to make a large
project for yourself and there's some
there's some work involved so you'll see
if you read the project specification
that we give a couple of ideas to get
you started so for example you might
want to do an extremely long exposure
maybe you want to take one of those star
trail like photos the point is not to
take an exposure that's just 15 minutes
or so like the demo that I had in class
or like the image that was in class but
to actually put some time and effort
into planning this this is not a trivial
photograph to take when you have to go
outside for two or three hours make sure
that you're in a dark enough location
far enough away from city lights and
that sort of thing that would ruin your
image and also the moon will be a factor
it just so happens that today I think
right now is the new moon so it's not
necessarily going to be ideal in a
couple of weeks time but you might still
be able to work with it there
fortunately this we only have two weeks
really to devote to this project but
still that's just some of the some of
the considerations that you have to make
there's other ideas as well some people
in the past have tried making their own
lenses so tilt shift lenses are types of
lenses that we'll be talking about you
also can have access to the 3d printer
that we have access to it's not going to
be it's that I would be wary in sort of
relying on that and sort of printing you
a fabulous lens but it will if you
really need to and if you have the
experience in modeling and doing those
sorts of things you'll be able to use
that to your advantage towards this end
but there's a lot more information in
the specification and please do read it
over there's a lot of inspiration in
there as well that we've tried to link
to for a variety of these things we'll
talk about some more ideas throughout
this particular class so the submission
tool of course is up and up and running
do continue to submit to that submission
tool and let us know if there are any
questions now the past few weeks or
rather just last week not the past few
weeks we've been talking about exposure
and last week we really covered the
three most fundamental things and tacked
on the fourth one somewhat
tongue-in-cheek by saying that light is
sort of the thing that really allows us
to that that the most fundamental aspect
that allows us to control using these
shutter and aperture and ISO values so
shutter speed of course was this idea
that we would be able to open that
shutter for longer and expose our sensor
to increasing amounts of light if
necessary if we have less light than
would necessarily be ideal but this also
has that sort of side effect of allowing
motion blur and how we can use that this
this idea of motion blur what it
actually means for our images the don't
recall also the difference between
motion blur
the subject so if you're able to keep
your camera absolutely still but you
have a subject that's moving around with
the long enough shutter speed you will
actually get some motion blur there the
distinction between that and also the
motion blur due to your camera so these
are all things to keep in mind as you're
working with shutter speed then we
talked about ISO and put sensitivity in
quotes because it's not actually truly
what's happening in the context of a
digital camera but it's a close enough
approximation for us to think of it that
way certainly for our purposes now and
but in a few weeks time we'll notice
that we'll be able to talk about the
distinction about what why this is not
actually talking about sensitivity and
we started building from this additional
exposure value the idea of controlling
this the side effects of these various
exposure values by altering one and
therefore being able to alter the other
so for example increasing the ISO
increasing the the so called sensitivity
of the sensor would allow us to have a
faster shutter speed to freeze motion
just a little bit more and then at the
end of class we started running out of a
little bit of time but I started talking
about aperture and the significant ratio
here which is that the f-number itself
which is what's what defines the F
number any ideas
yeah so focal length over diameter it's
the equation shown at the very top of
this particular slide but just shown in
sort of compact form the focal length
divided by the diameter where the
diameter is in fact the diameter of the
aperture inside which is not necessarily
the smallest piece of glass that's
inside of your that's inside of your
lens but it is actually a physical
device that will close down and reduce
the amount of light entering into the
lens very much like the iris in your eye
and the focal length is we discussed it
in a very brief way saying that this was
essentially the zoom level of your
particular lens and so if you wanted to
talk about the affects of aperture on
your photograph for example isolating
your subject from your background how
you really want to have an F number
that's as low as possible but there's a
variety of things that impact actually
the background blur including having a
very large focal length the largest
focal length you can and reducing the F
number as much as possible thereby
having a very large diameter aperture
will ensure that you get the most amount
of background blur for your particular
image and conversely if you wanted to
extend your depth of field and try to
have as much as possible in focus you
would do the opposite you're trying to
have use a wide lens and you try to stop
down which is another way of saying you
would try to reduce the size of the
aperture which is another way of saying
you would increase the F number and one
of the things that we didn't really get
a chance to talk about in depth is the
math behind the pinholes so we could
actually calculate the F number ratio
and as a result because we're able to
measure the distance between lens and
the focal plane you might remember that
focal plane icon that exists on camera
bodies we could actually measure the
focal length of the pinhole and by
calculating its f number figure out its
diameter and I we didn't have a chance
to talk about it last last week at all
but I did post the I did post the
document that goes into detail about all
of these things a little bit more detail
about F number the ratio itself why
those F numbers are sort of strangely
based they started F 1 and F 1.4 and
they go up through the scale of two and
two point eight and four and five point
six and so on each of those each of
those numbers representing a stop
difference in the exposure for our
particular camera and you might recall
that we talked about the a way of
simplifying your how you can remember
these numbers do does anybody remember
what that trick is what does that trick
that allows us to remember the major F
stops in corresponding two numbers any
ideas yeah exactly so we'll start at F 1
and F 1 point 4 and then what and then
you double each F 2 double 1 point for
it again F 2 point 8 double F 2 to get F
4 and so on and so forth now realize
that this is just an approximation it
breaks down after we get to about F 32
or so after this it does in fact become
a little inaccurate and so one of the
reasons why I refer you to this document
is because we talked about precisely how
these numbers are derived why these
numbers are seen to be so crazily spaced
the spoiler is basically that they are
separated by multiples of root 2 because
of this idea that we were dealing with
the ratio of the diameter rather than
the area of the of the aperture which is
really what is allowing the amount of
light to enter into the lens but this is
all demystified in this particular
document and the very end of it we
actually are able to calculate the size
of that pinhole lens that we were
talking about at the very beginning of
class and the spoiler is that we
estimate it to be about 0.5 millimeters
in diameter so I'm pretty proud of that
I think my needle work is relatively
good this is probably not precisely
accurate there's there's definitely some
error here because we did some rounding
especially with regard to how many stops
difference there was but this is close
enough with probably
about with an order of magnitude and so
I'm pretty happy with that results there
if you do have any questions do be sure
to take a look at that and ask away in
in section or of course ask the core
staff by email all right
so let's come back so we talked about
then the big four things that really
matter for our exposure which is the
amount of available light shutter speed
ISO and aperture and one of the things
that we'll really focus on today is this
first idea one of the most important
ones the amount of available light that
we actually have and how we can try to
improve or reduce the amount of light
that we have in the scene you might
recall some of the things that we were
talking about under exposure over
exposure sometimes it's both and these
are all very bad things went in in your
image you can really impact the power of
your image and there's a lot of things
that we didn't really get a chance to
talk about last week with how you can
actually fix these problems some of them
you can fix in software you could
perhaps take some several exposures if
perhaps you happen to be lucky enough to
be in a scene that is not changing very
much perhaps it's not perhaps it's just
the landscape scene for example and
really the only thing you have to worry
about is the Sun moving across the frame
or the moon moving across the frame or
the rotation of the earth causing the
stars to be slightly different but still
if you can if you do this fast enough
and take several different exposures at
different levels of brightness let's say
you take one that's properly exposed one
that's a little bit darker a little bit
underexposed and one a little bit
brighter later on in software you can
stitch them all together and if you've
done a good enough job maintaining your
camera's position then you can really
ensure that you get a nice results out
of that and sort of give yourself a
little bit more leeway this idea is
called bracketing many cameras have
support for bracketing already built in
and they allow you to quickly take three
five or even more images at various
exposures at various stops difference
from the center exposure which is kind
of an interesting idea and pretty neat
some of the other things that you can do
though are
in particular if you have for example
some an area of like in this upper-right
photo where you have both under exposure
and over exposure depending on the scene
perhaps you have for example a portrait
photograph that you're trying to take a
picture of somebody but the Sun is
behind them and the Sun is very
overpowering so you get this very dark
image of the person themselves and a
very bright image of the sky you can use
a variety of tactics like a reflector so
even if you just use a large white sheet
and reflect some of that sunlight back
to that person maybe you could use and
be careful about blinding them but maybe
you could use one of those Sun visors
for cars for example you know those sort
of metallic looking ones that reflect a
lot of light to keep the heat outside of
cars you can go to Walmart buy those for
five dollars use that as a reflector and
there's of course photographic specific
reflectors that have each of these
things they cost they tend to cost a
little bit of money but you can
certainly use a homegrown solution for
one of these ideas instead and provided
a little extra light to your subject to
try to smooth out the difference between
the background and the foreground in
that way and one of the other things
that we'll talk about today is fill
flash perhaps you can actually provide
extra illumination by using a lamp or
even a flash and to and give more
photons to that underexposed area of
your scene in that way of course the
power of good light is really what is
important choosing the time of day I
can't stress this enough I think I've
mentioned it at least once every week
and this week is no different but just
be sure you pick the right time of day
for your photograph it can really make a
big difference in its appearance and
your and how pleased you are with it and
of course there are ways that we can
intentionally over-and-under expose as
well we might have a studio set up where
we want to take pictures of objects
perhaps we are about to do eBay
something and we want to take a nice
picture of it so we might want to use
some techniques to try to overexpose the
background intentionally to give that
very isolated look to the object that we
are taking a picture of now all of this
discussion that we've had talk
about our control of the camera but what
you will find is that very rarely will
you set your camera to a fully manual
mode and set all of these three exposure
values is something that you want
generally our photography has to be a
little bit faster than that unless you
become unless you're already very very
skilled at this or unless you want to be
which by the way is not a bad thing by
any stretch of the imagination generally
what will happen is that we will rely on
our cameras automatic mode in some form
or another but still retain some control
over it and so even if you came into
this class using the fully automatic
modes of your camera on a regular basis
there's still this idea of the fact that
the camera has to record has to detect
the amount of available light in the
scene and adjust these same three
settings that we'd been talking about in
order to capture a properly exposed
image but how does this actually work
this is a technique called metering that
the camera does you might hear this term
within the context of cameras or if you
look at the specifications or even a
review of camera it will talk about the
cameras metering and this encompasses a
wide range of topics including how the
camera actually knows what settings to
use well really the camera is not very
smart in in many ways that does not have
the context of the scene
it does not understand the context of
the scene to try to decide for you what
those exposure settings should actually
be almost all cameras will try that have
automatic metering will try to make the
overall exposure this sort of middle
gray there is this idea of having this
this middle gray that is either called
18% or 12% grade depending on unhu' it
on who you ask which indicates the
amount of of reflectance of a particular
shade of grey and it's basically just
this and it's basically exactly what it
looks like it is just this middle gray
it's not too bright it's not too dark
the camera knows you might recall that
when we were talking about this sensor a
little bit the sensor has a limitation
to how many photons it can actually
accept too few and we won't see any
detail because it's too dark too many we
won't see any deep
because it's too bright and we'll just
completely wash away all of the detail
in that setting or all of the detail in
that scene rather so the camera knows
that it has to sort of expose for
precisely the middle of that range and
that is what is defined as middle gray
within the context of that camera so it
looks at the scene and it tries to
decide what the overall intensity of the
brightness in that scene is and it will
try to adjust those three exposure
settings to match this level of gray but
there's a lot of modes that can actually
that you can actually leverage to try to
give your camera a little bit more
context to try to help your camera
decide what this scene what is actually
going on in the scene and how it can
actually expose the photograph properly
there's a couple of different metering
modes one of them is called spot
metering and in spot metering it doesn't
try to take an average of the entire
scene but instead it takes only the
center 3% or so of the pixels or of the
scene itself as seen through the lens
and then it will decide that all of all
of that area right in the center of that
image should be the thing that should be
metered to middle gray and this can be
very powerful if you have a scene with
very high contrast you have some areas
that are very dark and in the shadows
and you have some areas that are very
light or maybe you have just one of
those things maybe you have an image
that is predominantly dark perhaps
you're trying to achieve a photograph
like this for example one of these two
photographs if you were to allow the
camera to try to expose this entire
scene for that middle gray what would
happen what would happen in the case
that we asked our camera to take a
picture of this assuming that every
portion of the image had the same
relevance the same importance to its
exposure how do you think the camera
would respond in this scene you would
under expose it yeah that's right
because there's areas here that are
extremely bright and are over
powering the image but it has no context
of what you are trying to do it doesn't
understand that what you're trying to
achieve is in fact this exact idea so
what it will do is it will try to make
everything this overall gray and what
you will notice is that your background
that should be white is actually not
white it's this gray kind of dark
muddled color and as a result your
subject is also underexposed and
likewise do we have a similar thing here
where if we take a picture of this with
just pure automatic mode just using
standard metering what we would notice
is that everything would be too bright
or overexposed as it tries to bring the
dark areas of the image brighter you're
therefore make your subject far too
bright so using something like spot
metering allows us to tell the camera
precisely what we want to meet her one
of the settings that you might have not
all cameras have this this spot metering
by the way but it can be a very powerful
feature in your particular camera one of
the things that we can do is look at the
scene ourselves and especially look at
the subject and sort of decide what
would be an area that's representative
of the middle gray of the proper
exposure it would probably be something
around here I would say just something
just sort of randomly picking a spot
because that appears to be sort of the
properly exposed middle gray area of the
scene so by pointing my camera with its
spot meter at that location do I know
that it will then meter the whole scene
just for that small point in the center
of the frame so this means that you will
sometimes have this idea of separating
your metering from your focus and this
is another really powerful idea that if
you actually don't use the same point to
meter your shot as to focus your shot
that you can achieve a lot so in this
particular example it is perhaps one in
the same to say that we do in fact have
something that we want to focus on is
the same thing that we also want to meet
her but not all situations are in fact
like that sometimes what you will see is
that if
person is wearing a white shirt for
example and they're outside and it's the
middle of the day that person will be
generally very bright and especially
their their shirt will be very bright so
perhaps what you want to do is to meter
on something on the background which is
more representative of the exposure of
this middle gray exposure and then
recompose your shot focus on the person
and then actually take your shot so
separating this Auto exposure from the
auto focusing can be a very powerful
idea so take a look at your camera
settings and see what if anything your
camera will allow you to do generally
cameras will have at least in auto
exposure lock which means that you can
point your camera at a particular
direction meter the scene for that that
it's that it's looking at and lock the
exposure and then change the the camera
to then focus and then take the picture
and so in combination you can then
properly expose your photograph and
focus on the thing that you wanted to
focus as well now contrast this with
another type of metering so again this
is spot metering and spot metering we
find typically only on higher end
cameras I would say it's I think it's a
little bit more rare to find it on on
pretty much every camera these days but
but center-weighted metering tries to
have a more balanced version of this so
whereas in our first example we had the
camera that tried to make everything in
the scene this middle gray it will take
in the center median Center weighted
metering the camera will look at the the
center of the image and assume that the
subject is there and this is actually a
pretty good idea for the way that most
people take their photos which is to say
that they will take their subject center
it and then take the photo and because
presumably the subject of the photo is
the thing that should be properly
exposed this center-weighted metering is
a pretty valid assumption for a lot of
the types of photographs that's we might
have taken in the past but now probably
as you're working your photography a
little bit more and
participating in the blog and getting
critique on your photos you're probably
noticing that one of the things that you
want to do is to not always Center your
subject in the middle of your frame
perhaps you actually want to put it off
to the side and provide a little bit
more power in that way this is of course
not a hard and fast rule but it's just
one of the techniques that you will
probably employ in the upcoming weeks if
not already and so Center weighted
metering then restricts you because it
is perhaps then not your subject that is
in the center of the frame but instead
the background which might be improperly
exposed in your case so take a look at
the metering modes that your camera has
it probably has something like
center-weighted metering it probably has
something like an all averaged metering
which is that very naive representation
of taking the entire scene and averaging
everything to some middle gray but many
cameras nowadays have something called
zone metering where it tries to
understand a little bit more of the
context behind the photograph that
you're taking and essentially what
happens is it will take the photograph
or rather it takes the scene as its
viewing it through the lens and it will
split it into hundreds or thousands of
zones and try to analyze each to try to
figure out what it is that you will
actually want to meet her so in this
case and it's very different a lot of
these zone metering x' tend to be
proprietary to the manufacturer so
you'll probably see some cameras boast
the 63 zone area of metering area some
of them will say oh we have two thousand
zone area it doesn't really matter the
number of zones doesn't really frankly
matter the difference between these
different types of metering what will
matter is how you understand and how you
learn and grow with your camera to
understand how the metering is going to
behave in a variety of circumstances and
how you can overcome its limitations but
anyway coming back to this idea of zone
metering there's a couple of things that
the camera will try to do to play some
additional context and try to do a
better job metering your photograph in
particular by splitting it into a lot of
zones it might be able to figure out
which of those zones are actually in
focus
and therefore which of those zones might
actually be representative of your
subject and place more emphasis on
properly exposing those zones those
areas of your image that are actually
properly focused perhaps it also takes
into account the distance to the subject
this might be this might impact then in
a similar way the the focus of the of
the the focus of the image rather the
subject of the image and how it should
alter the zones in that matter or if it
if it is able to understand this
information may be it will understand
that areas that are out of focus are
very bright and so that there are some
elements of backlighting to this this
photograph and try to compensate it in
that way but even so one of the things
that you'll notice as you work with this
is that even if you use your camera's
fancy zone metering it's still going to
be imperfect but all of the things that
you learned last week are not useless
anymore it's still very relevant to
understand what shutter speed does how
the shutter speed actually impacts your
camera how the f-number impacts not your
camera rather the image how f-number
actually impacts your image how ISO
impacts your image and altogether you
want to get that proper exposure while
still being able to modify each of those
and so typically so for example what I
tend to do is I tend to use like
aperture priority mode which allows me
to have control over the f-number
but allows the camera to decide what
shutter speed it actually should be to
properly expose the photograph this
simplifies my task just a little bit but
still allows me some control over the
camera and over the exposure but I still
am at the mercy of my camera's metering
in particular there's a lot of these
problems that can occur when the camera
does not understand the scene does not
understand what it is that I'm trying to
do and takes the exposure it with
incorrect settings so one of the things
that will be extremely important as you
work with photography is this idea of
exposure compensation almost always I
would say are you going to be using some
form of automatic control
unless you happen to be in a studio
setting with very controlled lighting
and then you want to always specify
manual control and have that continuity
have that consistency across all of your
photographs there are of course
exceptions to each of these things but
when you're outside and dynamic lights
or even taking photographs of an event
or of a scene where the light is
changing and constantly you want to have
some benefit perhaps some help in
actually achieving your your goal but
there's a lot of things that will
confuse this automatic mode including
things that have a lot of backlighting
anything that provides very strong
quantities of brightness or very strong
quantities of shadows
so snow for instance will be one of the
things that almost always trips up your
camera you can take a picture of it and
you may look at the picture on your
camera you may just be like okay that's
a pretty good picture of snow you go
home and you download it and you see it
and you still appreciate the image but
something doesn't seem quite right the
colors seem kind of muted perhaps maybe
the the the scene itself just seems a
bit dark and this is your cameras
automatic exposure getting it wrong and
making the overall exposure too dark
it's under exposing it and you need to
tell the camera that you want in fact a
brighter exposure so in this way we use
exposure compensation to overcome these
limitations so snow backlighting sunsets
sunrises if you happen to go to New
Mexico they have a white sands area and
this is exactly the same thing where we
have a lot of white in the scene and it
will in fact mess up our automatic
exposure conversely on the other end we
might have an area with lots of shadows
so if for example you happen to be
outside and taking a picture especially
here in New England in the winter and
people are wearing a lot of dark jackets
but you try to capture portraits of that
person that dark jackets if it's if that
person is sort of the predominant
subject in your photograph will be very
dark and will confuse your camera into
making the scene overall way too bright
anything that's dark really you're lots
of shadows I would wager that if you
were to take a photo of me standing
right here
for example just using your automatic
exposure because of the brightness of
the projector I would tend to be
underexposed as it tries to properly
expose the brightness of this projector
but perhaps that's not in fact what you
wanted so you can use this idea of
exposure compensation and we generally
see it as abbreviated as evey and this
very image in fact had to have some
amount of exposure compensation in order
to properly take it so on the left is
the image without any exposure
compensation this was not as shot I just
happened to know that because I was in a
in a scene with a lot of white that I
was going to have to increase the
exposure compensation to tell the camera
that I want it to be brighter so the way
to think about this is that when you're
in a scene that has a lot of bright
areas snow for instance or a lot of
white or very backlit for example you
will want to increase it you'll want to
increase your exposure compensation to
tell the camera that that scene should
be brighter than it thinks so if it's
bright turn it up if it's dark turn it
down and so on the left end is the scene
that as as would have been shot without
any exposure compensation all of this
all of the sand confused it in in a
certain way not to anthropomorphize my
camera but still it confused it in a
sense that it thought that the scene was
overall darker than it was even though
it was not in fact that dark so
increasing the exposure compensation by
a value of one which by the way
corresponds to one stop of exposure
compensation then doubled the amount of
light entering into my camera through
some variation of those exposure values
on that eye that I captured with my
camera and captured the proper amounts
of light to properly expose this image
so sometimes what you will see on your
camera is the ability to use exposure
compensation in increments of a third or
a half of a stop and this is actually
very important because generally you're
not going to use something as dry
as thick as one stop of exposure
compensation that's quite a lot and you
might recall that before I said that
what appears to us as being a doubling
or halving a flight is not necessarily
what it actually appears to be so even
though this again is not necessarily
representative of a true doubling or
halving in the number of photons this is
what the camera would have seen at half
the amount of light in that particular
scene so in other words we have this
dark scene we wanted to increase its
exposure compensation in order to tell
the camera that it was in fact brighter
so we added one stop of exposure
compensation to this image so if we
actually look at the the exposure values
used in this image we can see everything
that made it possible so it was at 1 1 1
or twenty-fifth of a second using F 2.8
to try to isolate my brother who is the
subject in the photograph a little bit
from the background using iso 200 and +1
stop of exposure compensation so before
I turned this exposure value to +1
before I added a stop of exposure
compensation
what would my settings what could have
my settings been so in other words if I
turn this back down to plus 0 evey given
the same amount of light how different
would my exposure settings be
so by pointing at this my camera at the
scene and asking it before I had input
any exposure compensation asking it to
tell me what the exposure settings it
thinks I should use what would it be
before adjusting it to be a stop
brighter
yeah exactly one sixtieth of a second
different is is a stop darker and so
that is perhaps one of the things that
my camera could have told me so in this
case that's probably exactly what
happened because I probably had
specified ISO 200 and I'd probably
specified F 2.8 and it was the shutter
speed that the camera was allowed to
vary so as I increased my exposure
compensation wait we got that backwards
it should be darker so it's one 250th of
a second that it would have told me
so one sixtieth of a second would have
been brighter so to put this so to
phrase this just a little bit
differently because I think one of the
things that confused me at first about
exposure compensation was why do I want
to add brightness to a scene that's
already bright that's not the correct
way to think about it necessarily the
correct way to think about it is how the
this the camera is actually looking at
this a bright scene again will tell the
camera or the camera will think that it
should make it too dark so what you want
to do is to pull the camera up and say
okay I really want it to be a bright
scene that is what I know that it is so
by adding a stop of exposure
compensation I'm then telling my camera
to let in a stop more light so whereas
my my shutter value at one stop of
exposure compensation was one 125th of a
second before recall that it would have
been too dark so it would be one 250th
of a second before I added that exposure
compensation and sometimes this doesn't
matter like in this case that shutter
speed is already fast enough for me for
me to be able to take this photograph
but sometimes you were right on the edge
of a hand-holder bull shutter speed and
by increasing your exposure compensation
by increasing your exposure value you
then are making the shutter speed too
slow for you to be able to handhold it
anymore
this seems to happen to me all the time
especially if I'm outside at dusk or
whatever whenever I'm taking a picture
in the evening sort of that ideal time
comes and goes very quickly with regard
to the nice amount of light that we have
from from the Sun but anyway as it gets
darker I have to try to adjust the
shutter speed and very quickly do I
realize that my shutter speed is just
getting too slow it's just getting too
slow and so if I have to increase the
exposure compensation because the scene
needs to be brighter then my camera
thinks it should be then I can get into
trouble more quickly in that regard and
conversely you might have the other
situation as well where you have a scene
that's very dark but it's already very
very bright outside so perhaps you're
taking a silhouette photo for example of
the sunset and you might already be at
an extremely fast shutter speed and
trying to turn down the exposure
compensation to tell it that you want
the scene to be darker because perhaps
you want to capture that silhouette
means that your camera cannot actually
take a photograph at any faster of a
shutter speed so these are these are
nuances these are nuances that you might
notice as you're actually working with
your camera in this idea and with this
idea of having exposure compensation but
the main takeaway is what we've already
described that you have a camera that is
going to try to meter using some form of
automatic mode a scene for some sort of
middle gray and because it does not
understand the scene because it does not
understand the context of the scene it
will sometimes get it wrong and you have
to give it an additional hint about what
you want for that scene if the scenes
should be brighter then the camera will
see it so in other words if you have a
lot of snow if you have a lot of white
sand or a very backlit area and you want
to properly illuminate your subject you
need to tell the camera to increase its
thought it's its thought process so to
speak to make sure that you are able to
get that subject properly exposed and
likewise if it's too dark if you have
something that's meant to be a very dark
game
lots of shadows in it and you think that
the camera will in fact take a picture
that's too bright then you'll turn down
the exposure compensation any questions
on exposure compensation either
compensating using a positive value or
compensating using a negative value all
right well this alludes to a couple of
the things that we've been talking about
with regard to metering in that is that
there are a lot of metering modes that
your camera might actually have and one
of the things that I've that I've
noticed and that you might notice as
well is that the the more the camera is
meant to be for very advanced very
professional users
the fewer metering modes it actually has
and the reason for this is because that
presumably the folks that use these
sorts of cameras that that's have a lot
of experience with their camera probably
already know how to tell the camera to
do what they want so they don't perhaps
need quite as much assistance and that's
one of the goals of last weekend this
week is to reduce your reliance upon all
these different metering modes that your
camera might have I've seen a couple of
my friends cameras and family's cameras
they have they they have literally
dozens of different modes now and it's
it's just gotten worse they have I think
there is several different party modes
there are several Beach modes there were
several ski modes I think there was a
ski mode in the snowboard mode in one
camera which doesn't make any sense
because it's all effectively the same
thing but there's no magic that your
camera is doing with these sorts of
modes it is just manipulating these
three exposure values that we've talked
about last week and some of these modes
might perhaps try to give a clue some
context to the camera so that it itself
will be able to do some exposure
compensation so if you were to say that
it was a ski mode or a snowboard mode or
you know any sort of mode like that it
might try to realize that you want a
higher exposure compensation so that the
snow will appear brighter but really
these are just specific tricks that the
camera will do and it's nothing
that you cannot achieve yourself in
perhaps even a better way by using one
of the the more basic automatic modes
you can still achieve the exact exposure
that you want and not have a reliance on
any of these things and have more
control over those side effects of each
of these exposure values on your image
so on the left is a meter dial for a
nikon d40x which is a few years old now
and we can sort of go around this whole
dial and figure out exactly what we
think the camera would do in each of
these cases so you'll notice that right
now the the little white mark indicating
which one is selected it's probably
selected at either a or s will start at
a which is representative of the
aperture priority mode which is the one
that I had alluded to earlier which
basically means that you get full
control over the F number you specify
precisely the F number that you want to
use and the camera will try to
automatically figure out the shutter
speed that would result from that based
on its own metering of the scene and
some cameras have automatic ISO as well
and some cameras do not require you to
specify the ISO in advance but in either
case it's still sort of the same idea we
still would get to set the ISO and the
camera would automatically pick the
shutter speed that it thinks would be
appropriate for that scene with the F
number that I had selected now
conversely there's the s mode on that
dial on the left which represents
shutter speed priority or time priority
and what this does is the opposite it
allows you to specify the shutter speed
that you want to use and it will try to
vary the the aperture the F number to
try to meet that shutter speed now one
time I really geeked out with all of the
all of the photos that I took and run a
script I wrote a script and ran a script
all of the exits date on all of the
photos to find out how many times I've
used various modes and I think it was
something like 99.6% or some
ridiculously high value do I use
aperture priority it was followed
closely by or not closely it was
followed this you know the second
distant the the distant second place was
a bulb or a manual mode because I was
probably taking a very long exposure
it's like more about bulb mode in just a
second
but very rarely do I use shutter speed
priority and the reason for that is that
your camera's your camera's lens has a
much narrower range of F numbers that it
can produce compared to the range of
possible shutter values so if your lens
is capable of taking photos with a
maximum F number of f/4 and by maximum I
mean a maximum aperture size the number
itself is of course very small here and
to have a minimum aperture size about
f-16 how many stops difference is that
between these two values
so from f4 to f-16 is how many stops
variants is it four so we go from four
to five point six five point six to
eight eight to 11 11 to 16 so we have
five stops sorry so that's that's very
close so we have five stops difference
between these two values now compare
that to the usual typical range of
shutter speed values on a typical camera
which might be something like let's just
be somewhat conservative here and say
one mm of a second even though most
likely it's much faster than that all
the way up to say thirty seconds so what
is the difference in number of stops
here this is I actually don't even know
this one that's when we'll take a real
while to figure out but we could say 30
seconds to 15 is one down to seven
seconds is two down to about three
seconds is three we could keep going you
know one and
down in point seven-five but already
we're at five we're not even at we're
not even that fast yet so this short
that takeaway of this is that this range
is much much higher than this range so
the range of possible shutter speed
values in terms of varying your exposure
is much higher for shutter speed than it
is for f-number and what this means to
come back to this idea of using the
aperture priority mode most most of the
time is that this means that it is much
rarer for me to encounter a situation
where my camera cannot given the F
number that I've provided to it it
cannot take a photo at a specific
shutter speed so sometimes what will
happen is the camera if it's way too
bright for example it will flash one
eight thousandth of a second because
that's the fastest my camera can
possibly go and it's warning me that it
cannot go any faster even though it
needs to and I noticed that by using
time priority and I really wanted to get
a specific time a specific shutter speed
out of that camera it was not able to
vary the F number enough to compensate
for that difference in light so the vast
majority of the time I use aperture mode
is that going to be the right option for
you I don't know but for that reason I
think there's sort of this mathematical
basis behind it that makes it a little
bit easier to use perhaps then shutter
shutter priority now the P if we are to
continue along going counterclockwise on
this dial the P is program mode it
basically allows you to vary both the
shutter and the f-number at the same
time so it decides on a particular
exposure value and it picks an F number
and it picks a shutter speed and then
you get to pick or you rather you get to
alter both of those one by one in one go
and this is reasonably nice but I like
to have just a little bit more control
than that and so that's why I tend not
to use that one alright so we keep going
full automatic mode this green portion
on the dial here means that the camera
is allowed to completely decide what it
wants in terms of all three exposure
settings and how that's how
photo will look as a result now there's
a no flash mode after that it's the
little no flash icon flash prohibited
icon but let's keep going we find that
the next one is basically a picture of a
person so this is presumably which mode
yeah portrait mode so what would we want
to do in a portrait mode what does that
mean what are we trying to achieve in a
portrait mode what would be the most
important settings for us to that we
actually care about in a portrait mode
what we're trying to get out here is to
try to decide what the camera is
programmed to do at each of these
different modes and again there's no
magic that happens here they only alter
each of these three exposure settings
but in portrait mode what might we want
I'm sorry the color the skin so we want
to try to make sure that they that the
subject is properly exposed and along
those same lines we want to try to make
sure that subject is isolated from the
background this is a picture of a person
so really what we want to focus on is
that person themselves including the
exposure of the skin but also the focus
yeah did you have an idea yeah exactly
so we want to have as low of an F number
as possible to have the lowest steps top
possible to really isolate the person
from the background and so even though
this is a fully automatic mode and
setting it to portrait mode the camera
is trying to prioritize the f-number and
try to make it as small as possible try
to make the f-number itself as small as
possible make the aperture as big as
possible to make sure that that person
is ISIL is as isolated from the
background as possible and then the
other things like the shutter and the
ISO are not quite as important in that
regard we can keep going there's a
landscape mode which probably confers
some ideas there there's a child so what
would the what might the child mode or
the baby mode or whatever that mode is
what that might imply
yeah so it probably is very similar to
sports which is might be the next one
it's kind of hard to tell because it's
upside-down but both of those are
probably fairly similar probably because
it indicates that the subject is going
to be moving very quickly it's probably
going to prioritize the shutter to be
very fast so what is the point of all of
this why are we talking about all this
it's just to point out that your camera
may have all of these modes and perhaps
more perhaps any number of party modes
and Beach modes and ski modes or what
have you but there's no need for you to
use these you can just by knowing what
it is that you want to achieve with the
those three exposure settings can you
set one of these other modes instead and
adjust the camera settings to reflect
your needs for that particular shot now
one so we talked just a moment ago about
how the more advanced cameras tend to
have fewer modes and really the reason
for that is the assumption that people
that are using these cameras do not need
all of this assistance with these
exposure modes and in fact that's what
we see with the camera on the right
which is a Canon 5d it's one of the more
expensive cameras on on the market but
it has so few modes compared to what
we've seen and we've talked about a lot
of these already now presumably they
include the green automatic mode for
whenever you trust the stranger enough
to give them that your camera and say
take a picture of me presumably that
person may not know too much about
photography or at least it's safer to
assume that they don't know how to set
the ISO and the settings on your
particular camera or even if they do
know how to do it what I notice I
actually really I my heart sinks a
little bit when somebody asked me to
take a picture for them with their
camera because almost always I have no
idea how to use it and so even though I
know what it is that I want to achieve I
have no idea how to change the f-number
or I have no idea how to change the ISO
on that particular camera so I'll just
quietly set it to the fully automatic
mode and do the best that I can with
that that's our little secret you won't
tell anybody right but a lot of these
we'd already
talked about the fully automatic mode
program mode TB is time priority it's
just canons way of saying time priority
this is the equivalent to the s mode on
the on the nikon on the right where
prioritizes you get to specify the
shutter speeds that you want and it will
try to pick the f-number a V is the mode
especially when I had a canon camera the
one that I use most frequently aperture
priority or aperture value that's what
the V stands for Animas fully manual
mode you get to fully select all of the
three settings for your particular image
and B is bulb B is the bulb mode that
allows you to overcome your camera's
maximum shutter limitation and the way
that it works is that when we discuss
this a little bit before but just to
review this idea when you set it to bulb
mode you get to pick the F number that
you want and you get to pick the ISO
that you want but in order to get the
shutter speed that you want you have to
push and hold the shutter button for as
long as you want it to be open now for
those of you that decide to attempt the
ultra long exposure shot for project two
this is going this mode is going to be
your friend except that maybe it won't
because in but maybe it won't is that it
might be a little bit of a pain to sit
with your camera outside in the cold for
two or three hours and trying not to
move your camera even though you're
holding down the exposure button you can
imagine how that will get very tiring
very quickly you might accidentally bump
your camera you might accidentally let
go and have to restart your shot so you
might want to consider using a remote
shutter release for your camera many of
which include a lock of some kind that
allow you to click the the shutter
button and keep it locked in that way
for any amount of time that you want
just don't forget to set your timer on
that camera any questions on any of
these oh I actually have a list of some
more of those modes so there were self
portrait mode so selfie mode there's a
party mode there's a candlelight mode
sunset mode fireworks mode Beach mode
snow mode
just way too much fortunately we don't
have to use any of those anymore from
this point on and in fact for all of the
projects from here on out we're
expecting you to use one of the modes
that you would find on a camera like
this either a fully manual mode or at at
least or perhaps at worst in aperture or
shutter speed priority mode one of those
modes be the ones that you should strive
for in your photographs it's required
for the problem for the projects from
here on out so be sure it's good to
practice with your camera and even
though you're using one of these modes
understand how it meters get to know
your camera a little bit to understand
the exposure compensation try to get it
absolutely perfect alright any questions
on any of that
so just to rehash we talked about all of
these three settings and how by
understanding these shutter speed the
ISO in the aperture we can overcome all
of the limitations no I shouldn't say
that we can overcome some of the
limitations of our camera we can
understand the limitations for our
camera and try to understand how we can
overcome those but let's take a quick
five-minute break and when we come back
we'll talk about how we can vary the
amount of available light to try to
overcome even more limitations of our
cameras all right welcome back so before
the break I just a little bit with this
ability to actually change the amount of
available light that we have in a scene
and perhaps it's that's a anti-climactic
measure to do or response to actually
say well flash is sort of the obvious
one now if you were to dig through the
archives of Etan back in the day it used
to be called e7 and if you were to dig
far enough back to some of the first
lectures that were actually posted
online you might actually hear me kind
of hate on flash a little bit and still
to this day I look at a flash like this
and I roll my eyes and I'm like oh
that's gonna be terrible there's still
some aspects about flash that are kind
of disappointing but a lot of them can
actually be fixed and really to devote
only a few minutes to flash like we're
going to do tonight is really a
disservice to it because there is an
enormous amount
of technique and skill and equipment
involved with flash photography that we
could probably create an entirely
separate course just on lighting just on
the techniques of lighting just on the
techniques of actually using flash
photography and in fact I think there is
there is one isn't there I think there
is actually a class on lighting and and
those techniques and so I definitely
encourage you if you are especially
interested in studio lighting or very
very careful setups involving even a
combination of natural and artificial
light that you look into that because
flash is actually a very powerful thing
that you can use within your images it
just so happens that the vast majority
of flash units that are out there that
are connected to cameras in this way
are just not super great though they do
have some utility as well now a lot of
these flashes are in fact automatic but
just like exposure we can actually set
them manually and we'll talk about what
some of those settings actually involve
now one of the reasons that we have some
problems with flash is this fundamental
property of light that's coming from a
single individual point source that's
not a laser
even though laser does happen a little
bit not quite as bad as this essentially
what this is saying is that we have
point source of light to imagine a light
bulb that's just sitting in the middle
of the room in a darkened room just just
sitting there there's no cover or
anything it's just a light bulb as we
get farther and farther away from that
light bulb if we step close to it and
then move farther away from it you can
imagine that the appearance of that bulb
is not quite as bright I mean imagine
you might have some sort of like
sympathetic pain reaction if you were to
imagine holding an illuminated light
bulb right against your face and looking
at it it would be kind of painful it's
really really bright but as you move
away from it very quickly does that
amount of light die off due to this
property called the inverse square law
the inverse square law is has has a lot
of implications for us as photographers
and also in in real life scenarios
essentially what it says is that for
every doubling in
the amount of distance from a point
source we lose a quarter of that
intensity of light so in other words for
every amount that we move away for every
amount that we move away from a point
source we have to square that to figure
out the reduction in light so if we move
from a particular distance let's say we
are one meter away from a point source
of light we move to two meters away
we're not just receiving half the amount
of light we're receiving a quarter
because of this inverse square law we
take that that that difference in our
distance 2/1 is a is it this is a
difference of two it's difference in the
power of two not a power of two
multiplication of two and therefore we
divide that we we square that and one
over that value is in fact the reduction
in light so if we now move whereas
before we were a meter away from that
light bulb we now move to three meters
away we're three times as far which
means that we get 1/9 the amount of
light and so this has a very relevant
idea in photography called light
fall-off
light fall-off basically describes this
precise phenomenon where we might have
rather than our point source of light
and rather than it being a light bulb
but rather than it being the Sun or
rather than it being some other light
source like that we're actually talking
about a flash unit so as you double your
distance from this flash unit you are
decreasing the amount of light by a
quarter and this has a huge impact on us
because as you might recall from all of
our discussion up until now sensors in
film has very narrow range of exposure
beyond which we will not properly expose
our image so a flash unit will really
function effectively at a very narrow
range away from that flash and this
produces a lot of the results that you
might actually experience when using
flash you take a picture of somebody
they have a silly grin on their face and
their face is overexposed and everything
behind them is really dark and it's
precisely because of this reason you
have the point source of light
immediately
above your camera and it is very close
to them as you were very close to them
and the background is not that much
farther but because of this inverse
square law we're losing that amount of
light very very very quickly so keep
this in mind this inverse square law
this is one of the issues that we might
have with flash photography and I'll
talk about some of the ways that we can
mitigate some of these problems in just
a moment but hopefully not to throw too
many equations at you at once all of
these are hopefully relatively simple
the one that we care most about when
we're dealing with flash photography is
this equation known as the guide number
and the guide number is just that it's
basically a guide to how powerful and we
don't really want to say we don't really
want to use the word power but it does
elude a little bit to the idea of how
much power a flash actually has and more
precisely what this guide number is
telling us is how far away in subject or
an object can be to still properly
illuminate that subject now how can we
reduce how can we reduce all of the
complications of a flash to just a
single number keep in mind that there's
a couple of things that actually matter
with regard to flash photography we'll
come back to this equation in just a
moment we call that we talked about the
focal plane of these cameras and really
what there was was this shutter that
opens and closes and exposes the sensor
or the film to light but we and what we
talked about in the first lecture was
that these flash units operate in an
extremely fast time speed an extremely
fast time range they operate much more
quickly than the shutter does on our
camera they might operate at one sixty
four thousandth of a second which is
really phenomenally fast compared to the
movement of the shutter as it exposes or
or not or doesn't expose the sensor to
the environment so what this means is
that in order for us to prop
use our flash units we have to set our
shutter to what's called the x-sync
speed and the x-sync speed is the
maximum shutter speed that your camera
can open both curtains and expose the
entirety of the sensor to the light once
that entire sensor is exposed the camera
will fire the flash and it will properly
illuminate the entire the entire scene
within your sensor if it's faster than
the x-sync speed if you set your if you
override the x-sync speed and and make
your shutter speed much faster than now
typical xing speeds are 1 250th of a
second one 500th of a second something
along those lines let's say you wanted a
faster shutter like 1 mm of a second if
you do that you will get a shutter that
looks like the video on the right where
you have both curtains that are
following each other one one curtain
that's opened and then another one
that's following quickly behind and you
will expose only a very narrow portion
of that image because of the flash that
you just took so effectively what this
means is that shutter speed doesn't
matter when we're talking about flash
photography now when I and let me
qualify that a little bit by saying it
doesn't really matter when we are
relying on flash as our primary source
of illumination perhaps we're relying on
other light as well and that complicates
things just a little bit but when we're
using just flash to illuminate our scene
shutter speed doesn't matter it doesn't
matter if it's faster it doesn't matter
if it's slow or fast as long as we are
no faster than that x-sync speed it will
still properly expose that scene because
the flash is hopefully properly
illuminating it so let's come back to
this idea of the guide number which is
basically just a measure of the distance
times the f-number the reason that we
can simplify it to this is that it
almost always assumes an ISO of 109 so
value of 100 which also eliminates that
from this equation as well so shutter
speed is not relevant here because it
doesn't matter
iso is assumed to be iso 100 and so what
this means for our flash is that in
order to properly expose something that
some distance away the way that we
change how powerful that flash is
quote-unquote is to alter our F number
so by altering our F number this is now
the last exposure value that we have in
flash photography in order to try to
expose something some distance away now
there are that we do have of course the
ability to change our iso as well and
then we would be able to alter how how
far away we are able to expose something
but let's remove that for just a moment
and talk about this simplification where
we're at iso 100 and we have a specific
guide number okay so let's talk about
specific values let's say that we have a
guide number of 13 meters or about 40
feet so this is a common guide number
again this is at iso 100 it's not
exactly 40 feet it's like 39 point
something but it's close enough so what
this essentially means is that for this
particular flash that has a guide number
of 13 meters or 40 feet that if we have
a subject that is 10 feet away I know
precisely what my F number should be I
have a guide number which is right now
I'll use P really units if you don't
mind 40 feet and we have a subject
that's 10 feet away times some F number
the F number should be 4 so F 4 means
that I will properly expose with a flash
with this guide number at ISO 100 and my
camera's set to the x-sync speed i will
properly expose something that's 10 feet
away so if something is 20 feet away
how much less light are they going to
get
so we double the distance which means
that that object that's 20 feet away is
now receiving how much less light than
my object 10 feet away
1/4 a two-stop reduction which is
probably going to mean the difference
between properly exposed and not
properly exposed so something that's 20
feet away in our camera that's set
through an F number of f/4 using a flash
with this guide number at all of those
other settings that we just alluded to
that we just talked about in the past we
properly exposed the 10 feet away and 20
feet away is just too dim for it to be
exposed now we can see how we can adjust
this as well what happens if I have an F
number of 2.8 instead so this was an F
number of 4 but if I have something at a
net value of 2.8 times this means that I
won't be able to expose something about
14 feet away so again it's a just an
approximation but this is a pretty
easily this is a pretty easy division
that we can do here now what's
interesting about this is that we also
get to see these two ideas our
discussion about F numbers and how we
have these sort of wild numbers that
differentiate by roots of 2 and this
idea that I just talked about before
this inverse square law the light
fall-off that happens extremely quickly
we can see that even though we are a
stop brighter in our F number our
distance has only increased by a small
amount it takes an additional stop in
order to properly expose something
that's 14 feet away and that's kind of
incredible I think and this really again
it has to do with just these two
fundamental ideas that we've been
talking about what the F number actually
represents and why it's separated by
by root 2 and also this light fall-off
so think about this and this is kind of
an interesting idea that you'll have to
that you'll have to take away one of the
things that you might want to consider
is now if I increase my ISO to 200 how
does that actually impact all of these
calculations well if I increase my ISO
to 200 I'll just do the takeaway here
and hopefully you can sort of think
about it on on your own is that if I
increase my ISO to 200 what I'm
effectively doing is increasing the
sensitivity so to speak of my camera by
one stop which means that at f/4 I now
am able to expose something at 14 feet
away rather than at 10 feet away so sort
of the easy way to compute the
difference in ISO and f-number is to
first look at the guide number at ISO
100 figure out how many stops way it is
in terms of F number and then sort of
push that to your new ISO and then use
that as part of your calculation alright
if there's questions about that I
realized that this is sort of even
though it's a relatively simple equation
there's still a couple of things to wrap
your head around so do give it some
thought and certainly ask questions to
the SAP list or in Section because I do
want to mention a couple of other things
as well now the way that you would be
able to capture extremely fast things
that actually occur without the use of
some extremely expensive camera like the
Phantom that is able to take thousands
of frames a second and just capture one
of those frames if you actually wanted
to take an image that was that fast that
was beyond the shutter speed of your
particular camera you can use the power
of flash for this recall that I said
that that the flash can fire in the
speed that is much much faster than your
fastest shutter speed typically we would
have at we have the ability to alter the
power of manual flashes
and if we just assume for just a moment
that at full power we have a flash that
operates at one one thousandth of a
second imagine how you as an engineer if
you were a flash engineer you might
actually try to change the power output
of that flash I would argue that one of
the things that you could do would be to
decrease the amount of time that that
flash actually fires so if I give off
full power at one one thousandth of a
second I can give off half power at one
mm of a second we call it we're talking
about flash here not shutter speeds
that's the distinction that we're making
but it's sort of the same idea right if
we're able to release half as many
photons then were then we're decreasing
the amount of light that were outputting
by a stop so what if we kept doing this
what if we went to afford them you know
one quarter power which would be one
four thousandth of a second and so on
and so forth now this is actually really
interesting because this means that we
could reduce the power output to its
smallest setting and we would not get
very much light presumably but we would
get a flash that occurs very quickly and
that is this idea that we can leverage
an extremely high-speed photography so
the task here is not to actually use is
to realize that you're not actually
using a fast shutter speed in fact you
want the opposite you want a room that
is completely dark except for your flash
that is not firing constantly obviously
but you want to have the flash that will
be your primary source of illumination
set it to its lowest power and set your
shutter speed to be very long just
capture all of the light and because
there is no light in the room it doesn't
matter we'll just be capturing darkness
until that moment that the flash goes
off in that instant at one sixty four
thousandth of a second or whatever the
maximum capacity of your flash happens
to be you will capture some events that
occurs at that time frame doctor dr.
Edgerton has a lot of wonderful examples
especially in his very early trials with
flash photography and now we've taken
this to extreme where you might
actually be able to scientists in the
past have actually captured light in
motion through a medium through through
this sort of technique which is sort of
kind of interesting but it also is kind
of a little strange that you have to
think about this in a slightly different
way that you want to use in fact a long
shutter speed rather than a very fast
shutter speed to try to capture
something very quickly but this in fact
is one of the ideas that you can use for
project two so the trick here is not
necessarily the setup though it is
obviously very important to have a very
dark room to have some event that occurs
very quickly that you want to capture
the trick is getting the flash to fire
it precisely the right time and doing
this manually is not going to work when
we're talking about the difference of
thousandths of a second you're not going
to have the reaction time necessary to
capture this precise moment in time
instead what you will typically do is
build a circuit that responds to noise
so for example imagine how this was set
up there was a camera in a dark room
there's a flash unit there was a gun off
to the side an apple the the gun was
very carefully aimed at the Apple
somebody fired the gun there was a loud
bang from that from the from the bullet
exiting the the weapon and after some
amount of time it actually went through
the Apple so there was a circuit that
dr. dr. dr. Edgerton devised and which
you can actually recreate on your own
that responds to noise and then fires of
flash tails the fire to flash after a
certain delay so I'm sure they did a lot
of sort of gets in check to try to
figure out exactly the right amount of
time delay to actually fire the flash
after the sound of the gun going off
this is precisely the idea that you can
implement and it's kind of a cool thing
to know that you can do it yourself so
if you're at all electronically inclined
the circuits I don't think is that
complicated we link to some descriptions
and ideas on the project but do take a
look at this because you can also
generate fantastic images yourself now
what can go wrong with flash of course
or all of the things that you have seen
in the
with your own images with other people's
images or what have you
do you remember that picture in white
sands of my brother that I was using as
an example for exposure compensation
well that's him just twelve years ago in
the same place by the way but this was
well before I understood all of the
values of exposure and I was like okay
it's a dark place I'm gonna use flash
but there's a lot of stuff that it went
wrong in this particular case can you
identify some just tell me what I did
wrong here right now well I mean I
definitely did some stuff wrong but tell
me what went wrong with the flash in
particular it's all the typical flash
stuff can you can you name some redeye
perfect anything else that's the moon
actually back there the light behind the
object is in fact the moon but obviously
that's not I mean if you have to ask
it's not very well captured I mean
that's but if you look just very close
to the moon you can see something weird
about the the clouds right there's some
motion blur in the clouds for sure but
is there anything else there's one more
thing that's bad about this okay there's
several things it's out of focus but
ignoring the focus sorry this so yeah so
the the shutter speed was long which is
probably accounting for the motion blur
and the clouds now I was hand-holding
this and so that sort of accounts for
some of the the blur and my brother and
sister and also the blur and the clouds
but there's one more thing which is a
little subtle which is this harsh shadow
behind them so you can see that yeah
there's a little bit of sand that's
illuminated very quickly because of
light fall-off we don't see any of that
and that's arguably the cool thing about
this shot or about this location is
being able to see that sand and so all
of that then what was neat about this
was in fact destroyed by the use of
flash so how can we overcome this well
think about what's happening with the
eye the when you cause a flash to fire
it's generally very close
to the camera itself to the lens itself
and so when it fires it causes light to
go through the iris of the person that
you're photographing bounces off the
retina comes back and you're essentially
seeing the back of their eye you're
essentially seeing the red of their eye
so this is harsh bounces off the retina
yeah there's redeye reduction but that
stuff never works especially because
it's very dependent based on age and
physiological differences between people
some people actually respond better than
others do that pre flash idea of some so
the way that some redeye reduction works
is that it fires flash and then
hopefully tries to constrict the iris a
little bit so that this reduces the
problem a little bits of the light
actually bouncing through the back and
then back to the lens but doesn't work
it's terrible doesn't doesn't ever work
but the way that you can actually
eliminate a lot of these problems is to
actually move the flash off the camera
so part of the problem was that what you
had was this flash that because of its
very narrow angle compared to that of
the lens let's say we have a you're
gonna see my wonderful artwork here I
have a person have a camera oh boy this
is gonna be bad and you have a flash all
right so this flash comes over here
comes into this person's eye and then
reflects back in that way so this angle
right here is extremely small especially
when you have any sort of relevant
distance it's basically zero it's
essentially zero that that light is
being sent in and directly bounced back
into the lens so if you move the flash
off the camera even just a few feet what
happens is that you have this flash
that's up here on this sort of
silly-looking device and it increases
the angle by a great deal so what this
means is that this reflection comes in
and it bounces down and doesn't actually
enter into your camera's lens so moving
the flash off the camera is a great way
to do
this but this also fixes that issue of
the shadow where the reason that we have
the shadow is that the lens or rather
the the flash was just off axis to this
person so it was causing this shadow for
this person that was very close behind
the person and our camera was capturing
that shadow by having a flash unit
that's distant from the lens it it still
has a shadow obviously it's still
casting a shadow but it just so happens
that that shadow is at a much much
harsher angle and you don't actually
generally capture it within your camera
so it's sort of interesting that having
something that looks like this can
actually solve these particular issues
so there's a couple of things that you
need to do you need to generally have a
cable that can actually fire the flash
remotely
there's even fancy wireless devices that
allow you to have the camera or rather
the flash completely off the camera
which is kind of cool a variety of other
techniques like this now a couple more
things I want to show you one of them is
this context of imagine you have a very
long shutter speed you have and by that
I mean you have several seconds so you
open the the shutter you fire the flash
at some point and then you close the
other shutter but the question is when
in that time that those two curtains are
open do you actually fire the flash do
you fire it at the beginning do you fire
it in the middle you fire it at the end
does this actually have an impact on
your image and as a matter of fact it
matters a great deal when do you want to
see if you have a very long exposure and
you have some motion in that image when
you fire the flash in that exposure
makes a huge difference as to what that
image actually appears so this is a
little counterintuitive but if you
actually fire it as soon as you open
that first curtain think about what
happens you open that first skirt and
you fire the flash you get some
illumination and then that object
continues to move for the duration of
the exposure so what you actually see is
sort of the opposite of
you would expect you get you capture the
moment in time you capture the exposure
of that object at the beginning of its
motion throughout that shutter that
throughout the shutter the time that the
shutter was open so it almost looks like
it's moving backwards which isn't
necessarily what you want what you want
perhaps is to have second cut second
curtain sink or rear curtain sync there
since they're synonyms which means that
you open the shutter some action happens
that you capture and then you fire the
flash at the last instant right before
you close the second curtain and because
that action had occurred throughout the
time that the shutter was open and then
you finally capture the final exposure
at the very end of it does it actually
appear as though objects have that
proper movement forward through time now
there's a lot of other cool stuff that
you can do with flash like stroboscope
s-- it's actually this very idea that
allows you to have to exceed the x-sync
speed on your particular camera imagine
if you can just fire the flash many many
many many times in a row at relatively
low power you could still compensate for
those two curtains moving without
exposing the entirety of the sensor and
exceed your ex in speed sometimes this
is useful some flash units you can
actually even though they're older they
have full manual control and you can
actually use them on your camera but do
be careful some of the older ones have
very very high voltages across the
contacts that actually fire the flash
and these high voltages can ruin your
digital cameras if it is not ready for
it so there is a way to actually check
will post the link on the course website
it's called safe sync it's just one way
of checking it's not necessarily the the
the I mean the really the way for you to
tell is to measure it but you can sort
of search around the Internet and try to
be sure that is actually going to work
for you this flash the Vivitar 283 is
actually very popular flash for people
that are just getting started with flash
photography and I recommend it if you're
going to do that
now Phil flash is perhaps one of the
most important things when we're talking
about flash in terms of what we can do
with it now without having to get fancy
with lighting it provides extra
illumination for what might otherwise be
a harsh exposure backlit exposure this
just so happens to be a very fortunate
coincidence that as I was taking a
photograph of this of this roller
coaster the flash from the roller
coasters camera you know that takes
picture of everybody happened to fire at
exactly the same time it's very lucky
capture and this did a current one three
two hundredths of a second and there's
my brother again sort of hiding so it
was very fortunate that we were able to
do this now in the last few minutes of
class I did actually want to discuss
just a couple of things one of them are
not discussed a couple of things but
actually to sort of launch us into this
idea of actually being able to discuss
some of our photos in class and I wanted
to start out by presenting some of my
own images for critique so I have this
image here which I took in LA some
number of years ago and really the goal
of this is to do like an in-person
critique and so I have one of mine here
that I want to sort of get critiqued and
sort of talk about it a little bit and
then in the last few minutes please do
sort of stay for just a few minutes over
so that we can actually talk about one
of your peers who has very kindly
allowed us to show one of hers so what
do you think John you want to get the
ball rolling can you make any comments
can I pull screen it that is an
excellent question oh yeah I know how to
use a computer so I apologize it's a
little dark here but maybe that's in
fact a problem with the image
actually you do you want to like come up
here I have a little microphone oh wait
I have to turn this on can everybody
hear me out there cool
overall I like the photo the lighting
from the city itself is really
interesting the foreground is a little
hard to discern it I'm assuming there's
nothing important there for me to look
at but I'm not positive because it is so
dark I do like that you're sort of using
that I'm assuming it's a tower a tower
or something I like that you're sort of
working that into the frame and working
that into the picture a lot of times
when there's something in the way of
what you're trying to look at in this
case Dan was probably trying to get a
good picture of the city lights but he
happened to be standing near that that
that Tower
right so instead of trying to avoid the
tower here's like well how can I work
that into my frame how can I use it to
make my composition more interesting so
I think that that makes it pretty cool
actually that's very perceptive that was
sort of the point was that I wanted to
mix the two ideas of actually having the
the city in the frame but I didn't just
want it to be a standard sort of long
exposure shot of the city itself I also
wanted to sort of capture that and one
of the things I liked was this Bush
that's sort of swaying in the wind a
little bit and you can sort of see it
but it's very subtle it's like a very
subtle thing but you can in fact see
that there's some motion there there
cool so from this thanks time so from
this I actually adjusted my position
because I thought well okay you know it
it looks more like a mistake than it
does an intentional photograph so I
tried moving a little bit and despite
all of the sort of warnings that that it
had I decided to try this instead so any
thoughts on this particular adjustment
on this image so now what I've basically
done is I've moved myself and my tripod
into this the base of this tower and I'm
now trying to capture specifically
perhaps the the warning sign above and
the still capturing the lights but
trying to frame it's a little bit better
any thoughts on this
yeah so if I can rehash that for those
watching at home I think there were sort
of three major things that I took away
I'll try to try to capture them all one
of them that she mentioned last was that
the sign even though I tried to capture
it was in fact to cut off and so that is
in fact distracting that again if I can
paraphrase your words at least to me it
looks a little this it looks it looks
distracting but also it looks like an
accident
like I didn't notice the sign perhaps or
that I didn't mean to include it as part
of that because otherwise perhaps I
would have taken a step back to actually
capture that some of the other things
that you mentioned or that the the
framing was perhaps a little bit better
overall because now it doesn't look
quite so much like oh it just so
happened to be there just so happened to
be a tower right there that I was trying
to capture and I've actually like moved
within it so be sort of capture that
idea a little bit more and also that I
think one of the other things that you
mentioned was that it's just still so
dark down here that it really gives it
off this air of like not important this
area of the image is in fact not that
important at all so why did I bother
capturing it well I don't really
remember I'm to be honest at this point
what I was trying to do with these two
shots I just remember seeing this
structure and thinking that it looked
really neat with regard to the city but
it was really really difficult to sort
of capture both this this or there's
really three things here that that I
think I was trying to capture one was
the the city itself but also the fact
that this was a part within the city
this was a long Mulholland Drive on in
LA um but that also even though I was in
this park we still couldn't get away
from the fact that there was this this
industrial aspect to it the city still
had its its presence in this area and so
part of this was a little bit of the
bias that I had coming into this this
photo and what I ended up with was this
there was this third photo where I tried
to really eliminate of some of the
distraction and try to focus on the
structure itself so this is from the
same tower the same everything except
that now I've altered my perspective a
great deal to capture the tower itself
and also you can still see hints of
these other aspects that I had mentioned
you can still see a hint for example of
the glow of the city below you can still
see a hint of the park that was there
but also I think I really enjoy like the
the geometry that came out of this the
the analysis of that that we can do of
the geometry of the tower itself and
that we can actually see what it's used
for before unless you read the sign
perhaps it wasn't totally clear what
that tower was I mean you know we could
probably guess it was an electrical
tower but it wasn't super clear but now
it's a lot more clear what's going on
but this is in fact power lines
we're probably power lines and in that
it sort of gives that a little bit more
context as well so this really what what
I wanted to do here was just to show
some of my own work and so my own
thought process for going through this
and so this sort of conversation is
something that I want to have on a
grander scale as well that we have on
the that we have on the blog but also
here in lectures and when possible in
person in sections or even online
in sections but I'm not expecting we're
not expecting you to submit sort of you
are you're evolved your evolution of
your photos as you actually work on this
this is just sort of one insight into
the way that I worked a particular image
as I actually did this so if you will
allow it's just a few more minutes
katelyn actually decided to show us one
of her photos and she is decided to give
allowed us to critique that as well so
do you want to come describe this for us
oh one second one second when we give
this to you
well it's for the folks at home as well
so I work first School District in our
homecoming was this week so I jumped out
onto the track and the marching band was
coming on and the conductor climbs up
onto this big ladder and I just really
liked the balance between everyone
looking up at him and him kind of
isolated on the sky up there I struggled
with going back and forth between color
because homecoming so much about school
colors but the ladder was bright yellow
and the sky was kind of gray so I
thought making it black and white kind
of helped with the classic as a band but
I'd be interested to hear what you guys
thought Thanks so I'll give some some
thoughts first um normally I I don't
think if I'd done my rant yet on black
and white normally I rant about black
and white because I think it's I think
it's overdone and I think some people
tend to do it just to make it look more
vintage or impactful in some way but I
think there are times when it's actually
very successful and I think this is one
of them for a couple of reasons one is
that it is it is actually it's very much
black and white it's very simplified in
that in that color screaming back black
and why do you have the the white sky
and the the black conductor at the top
but yet there's the the ladder itself
which has some very bright tones to it
that's still sort of it's it's very well
split in all of these ways there is this
sort of idea that the bottom three
it's very busy but there's a simplicity
to the very top of it it's I think it's
really well done overall and I enjoy
this image I enjoy this image a lot I
like it that it's also squared up very
nicely with the the sort of the middle
line here and that it just is it seems
like no accident that they were
practicing in that manner and it's neat
that you were able to to capture that as
well other thoughts yeah would you mind
saying some words it's just that I don't
have to rehash everything for the folks
watching from home well I guess that
what I appreciate one is the moment this
hands are up it seems to be the
appropriate moment to take this photo
because I think you would lose something
and the black and white makes sense
because of the amount of detail and also
the forms that appear like I'm drawn to
the lines of course the ladder the rungs
and then the lines in the field and then
the lines on their jacket the lines on
his clothing and then the circles with
the drums and then the zero so those
become very important and I think that
color I'm imagining the color of just
the uniforms and the drums long would
distract us so I think works really well
and but the hands that moment we isolate
him so this idea that you have a crowd
but yet he's alone and that that's a
really interesting moment too and a nice
sort of contrast of subject matter so I
really appreciate this thank you yeah
it's sort of interesting that there is
there's hints of project one in there
there's the hints of the the circles
here there's hints of the the rectangles
and that's sort of neat that that that
idea is sort of exists if not
intentionally at least accidentally and
actually that's a really good point that
what you're making about the hands
because it it's it's it's only it there
is this there's the sense of control
that that hand gesture has
that may not have been there if the
hands were a little bit we're a little
bit lower yeah oh I'm sorry one yeah one
cup yeah I'll go ahead I was just saying
I wanted to say something nice now that
I was so critical about the last image
right I really like this too and I think
that there's a an awesome juxtaposition
between the symmetry of the image like
the perfection of all the lines and kind
of the absurdity of where where this
conductor is positioned seemingly in the
sky and there's also some great leading
lines that really pull the eye to where
you should be looking in the image the
converging lines of the latter the
converging lines on the field all draw
your eye to the middle of the image
which is truly the focus of that
conductor in the sky I think that was
well thank you you had a comment
when they said this picture for some
reason I thought this picture is for the
project of the shapes the triangle
because in here's obviously the center
is the triangle DeLaughter and also his
hands in this guy so it's like a double
triangle and I was surprised that it was
what is your intention to use this for
project one okay
oh so for those at home she said that it
was it was not her intention to use of
project one it just so happened to be
there so it's so there's been a lot of
phrase for this image and rightfully so
it's a it's a wonderful beautiful image
is there anything that we could do to
improve it and this would maybe
realizing that we may have to nitpick a
little bit if you'd be okay with that
but is there anything that we can try to
do to say this image is great let's make
it better or is it not possible yeah
John so I first just want to say that I
really like the photo and I think it's a
little bit subtler than in Dan's but
there's a really great use of geometry
here as well it's a little subtler and I
love this photo because it there's kind
of a rule in photography like a general
rule of thumb it's like don't center
stuff but this is I think great because
it is centered so for every rule you
throw it away half the time anyway
but I think a helicopter would have made
this photo yeah yeah that's my typic
anybody else no actually that's that's
important it's interesting that you say
it's centered because my first reaction
to this is that it's not centered with
all of the essentially all of the action
down in the lower third it's it's I mean
I think there's there's kind of an
argument to be made that yeah the the
conductor is centered horizontally but
vertically there's nothing there's that
expanse that's a good point it doesn't
feel centered it's an even distribution
cool first of all I love the I love the
picture
I also would generally have a bias
against black and white but this is this
is a vintage shot I mean I looked at
this and I at first thought what's you
know what's Charlie Chaplin doing on
that on that on that ladder there it
looks like it could easily be an old it
taking a long time ago so then this is
totally in nitpick it would have been
cool if you had dropped down two feet or
a foot and a half and you had gotten
that guy right in the middle below the
conductor his face through the ladder
rungs now I this had to have come
together really quickly and it's awesome
that you got the hands so it's totally a
nitpick but since what we're doing here
is nitpicking it would be cool if the
guy's face we're visible through the
latter runks yeah that's that's
interesting that's also the sort of the
one thing that I that I had in mind was
that just to just to move it just so
slightly there might be an air of
mystery involved with that with that
player but because he's not necessarily
the subject and you know but but that
but again we it took all of us staring
at it for this long to really again I'm
sorry I kept going back and forth but I
think there's a tension that you can't
see the eye and you can't see his face
and so I think they parallel each other
in such a way that to take that away
would take something some kind of
tension Oh interesting so an opposing
view that they are yeah an opposing view
that it's actually more symmetrical in a
way to have that person blocked by the
conductor and we also cannot see the
conductor that's actually yeah really
interesting and also while I was
thinking about that same idea if you
were to change your perspective by a
foot or two it might just totally ruin
everything else you might just change
the perspective just enough that you no
longer get the feeling out of this that
you as you actually do let's do one more
I just thought it might be interesting
is this pictures vertical and there's a
lot of the sky that doesn't really do
much although
I mean it's a great picture I love the
picture but to maybe see it as a
horizontal shot to catch more of the
marching band I don't know how much more
the marching band there is but maybe
catch a little more of that would be
interesting Oh interesting so to reduce
the to reduce the prevalence of the sky
a little bit and get some more of the
band yeah that would be an that would be
an interesting perspective to see I
think what the thing that struck me one
of the things that struck me primarily
about it was in fact that expanse of sky
and just how sort of smooth it was so
it's very it would be hard for me to
know without sort of seeing it what what
that would look like anyway thank you
all very much for participating and
allowing us to go over for for a few
minutes if I hope that you will in fact
send some so that we can do this same
thing and in lectures in the future and
we will do better about the timing for
that but if not then do at least do this
within your sections as well and I think
this was a great way to see the work
that we're all doing and being able to
comment on that so with that thank you
all very much for coming we'll see you
again next week