Nuke; Basic Workflows; Colour Management - Part 2 Video Lecture | Create Visual Effects with Nuke - Professional Skills

now let's take a look at the viewer and
the viewer Lud I'm going to expand the
viewer to fill the whole frame again and
here's the viewer let pop-up right here
this is where you select which let will
be used in the viewer keep in mind this
correction is applied only to the viewer
and the original linear image is
untouched srgb is the default which is
typical for a workstation monitor and
you get a curve that looks like this if
I turn it off
you can see we're looking at the linear
image and it's way too dark so you can
see now what this viewer LUT is doing to
brighten the image up
remember earlier we talked about
brighten the image up with a gamma
correction so it looked right on a
monitor there it is you could also
choose the rec 709 lat
which would give you a rough
approximation of a broadcast monitor if
you want to connect a real broadcast
monitor to nuke it'll require a special
video card setting the viewer back to
its normal size we'll take a look at the
right nodes to show you how the right
node works I'm going to clear the
properties bin first so we start with
the marcy 8-bit TIF image we do all of
our compositing operations in linear
space and now the right node were
getting ready to write it out to disk
nuke will decide what kind of color
space LUT to use depending on the type
of file name that you use so let's say
I'm gonna write Marcy out as a TIF image
so I'll type Marcy thought TIF and I'll
say save and look what nuke has done
said file type is TIF it looked at this
extension it said the file type is TIF
the data type is 8-bit so the color
space gamma correction it's going to use
is the srgb and of course you can change
that if you wish if I had said that this
was going to be a cine on image it would
say file type is cine on again looking
at the extension it would say the file
type is sitting on and the color space
correction let it would get is the cine
on if I said that this was going to be
an EXR image and nuke would detect that
was the file type and would use a linear
LUT so nuke looks at the file name
extension you apply to your files in
order to determine what the output LUT
should be so to summarize nukes color
management workflow will expand the
viewer to fill the frame the read node
backs out all baked in gamma Corrections
to restore the image to a true linear
light space nuke performs all of its
computations on the linear light version
the linear version goes to the viewer
where it gets a viewer LUT to make it
look nice and then the linear light
version goes to the right node which
assigns a gamma correction just as it
writes it out to disk now that we've
seen
the complete workflow for nukes color
management let's take a look at where
the let's live now the term LUT actually
is an acronym LUT which stands for
lookup table for those of you they've
never worked with a lookup table before
let's take a quick look we'll select
Marcy go up to the color tab and add the
color lookup node the color lookup node
is actually a lookup table
I'll select the master curve and show
you how it works the incoming code
values come along this line down here on
this edge they go up meet the curve and
come out on this edge over here so this
is the input code value side and this is
the output code value if I make a change
in the curve like I take point five up
here to 0.8 now code value 0.5 will come
up to the curve and come out as code
value 0.8 likewise
point 1 will come out as point 2 and
point 9 would come out as let's say 0.98
all right we'll get rid of the color
lookup node and take a look at the lots
in Nuuk put your cursor in the node
graph and hit the S key to bring up the
project settings the project settings
have four tabs we want the LUT tab and
this is where all the let's live in nuke
the first LUT a linear LUT does not
convert anything to linear it's a no
change lot some people call it an
identity let others call it a unity LUT
so if code value point 5 comes in 0.5
goes out and the image is completely
unchanged here's the srgb LUT fact I'm
going to add the linear LUT to the
display so we can see them both together
remember the incoming images have a
gamma correction that curves like this
the srgb gama curve curves in exactly
the opposite direction resulting in the
linear image that nuke uses for all of
its compositing so the srgb LUT backs
out the baked in gamma now some images
might come in as a rec.709 we would use
this curve the cine on LUT is used to
convert 10 bit log cine on or DPX images
to linear the panel log converts
Panavision log images to linear read log
converts a red camera log images to the
linear VIPRE log converts the VIPRE log
and red space is a lot provided by the
red camera company the next item of
interest on the LUT tab is down here the
default LUT settings so up here is a
list of all the lets anouk but down here
is where nuke
signs where they are used the default
monitor LUT affects postage stamps
opengl and non viewer displays such as
this postage stamp right here we're
going to zoom into the Marci postage
stamp right now it's getting the srgb
lot same as the viewer so the Marci in
the viewer and the Marci and the postage
stamp looked the same but if I go to the
monitor LUT and say for example set it
to linear you see the postage stamp
turned dark that will put that back to
the default srgb the rest of these
default LUT settings are used by the
read and write nodes so when the read
node sees an 8-bit file such as the
Marci TIF file it's going to use the
srgb LUT or in a write node if you're
writing out a log file it's gonna use
the city on LUT if you read or write a
16-bit file it's going to get the srgb
LUT unless you set it to something else
put that back if you read or write a log
file be that cine on or DPX nuke is
gonna use the cine on LUT and if you
read or write float files nuke is gonna
use the linear LUT and you'll recall
that is the no change LUT because linear
EXR files are already in linear light
space the last thing we want to talk
about here on the LUT tab of the project
settings is how to create your own
custom LUT which is very easy to do
first you select the little plus sign
which says I want to add a lot now you
give it your name we'll call it my LUT
say ok it's now been added to the list
this is your LUT curve select it add a
control point make some changes in it
there now I've created my own custom LUT
and every read and write mode in nuke
will use it for example I'll come down
to the 8-bit files which you recall
that's what this read node is using here
cuz the Marcy is an 8-bit TIF pop this
up and there is my LUT watch Marcy
change when I select it bang okay so
that's really ugly so let's put that
back to the default
RGB which
much better than my lot and when you
save the nuke script your new LUT is
saved with it because of the colorspace
conversions in all read and write nodes
in nuke there's a special consideration
whenever you're working with
premultiplied cgi images like this jet
here okay well zoom in on this guy I'll
show you
he's a four-channel CGI premultiplied
image and now we'll take a look at the
composite and I'll open up the read node
the read node has this additional option
right here premultiplied as you know any
color Corrections or color space
conversions on a premultiplied image it
must first be unpromoted before the
operation and then re multiplied or pre
multiplied afterwards with this button
you're telling nuke this is a pre
multiplied image in the read node and it
must be unpromoted lied before the color
space conversion so I'm going to turn it
on and look at the huge effect it has on
the composite if you fail to enable the
pre multiplied feature your composite
edges will be too dark we have the same
exact setup in the write node I'll come
over to the Images tab and I'm going to
add a write node off to the side here
and right here color space default
premultiplied you would not turn that on
for the finished composite however if
you were rendering out a four-channel
premultiplied image like this if this
was what you were writing out to disk
you would definitely want to turn that
on if you don't the rendered image to
disk will have dark edges when the next
guy gets it at his workstation so heads
up when working with premultiplied CGI
with nuke