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[ 101 ]Gradient Map applied instead. The variation is nearly entirely
gone because the luminosity is the same for all the colors.
Now that we know the difference, let’s build a cus-
tom CLUT (if you’re not familiar with CLUTs, you should
certainly try out the built-in presets to get a feel for what
results are possible). I want to put together a kind of hilari-
ously complex adjustment layer stack just to demonstrate
the potential here.
Note: To access the CLUT presets in Photoshop,
click on the Create New Adjustment Layer icon (half-
black, half-white circle) at the bottom of the Layers
panel, and choose Color Lookup. In the Properties panel
(Window>Properties), you can find all the presets in the
3DLUT File drop-down menu.
Showing a comparison of a gradient map and
a CLUT over an isoluminous gradient band.
USING A TEST FILE
For whatever reason, I felt the need to add all these adjust-
ments to get the final color version. Some of the adjustment
layers have blending modes, some have different opacity
values, and all of them have been tweaked in some way. The
point is that however I got there, I have the results I want for
this particular image from a collection of adjustment layers.
If I’m shooting a series that starts with roughly the same
colors and exposure settings, then I could just immediately
export the CLUT file. But there’s a shortfall here that we can
address with a simple test image.
Once I export the CLUT file, I can’t change it. Any mod-
ification that I want to make permanent means I have to
start over and generate a new file. I either have to rebuild
the adjustment layer stack, recall it from being saved
somewhere, or I have to use the CLUT and add some more
adjustment layers, then save out a new file.
Why would you want to change the look? This would
typically be done when the image you used to build the
CLUT lacks some set of colors that may come up later in
the series of images, even pure black or white. Including
a color chart in the starting image would help alleviate
this. Basically, doing this check helps your final CLUT to be
more flexible down the road. If you’re building it only for
a specific project where you know the input will always
have the same range and tonality, then there’s probably
no need for the extra step.
To spare you that repetitive
effort later on, apply the layer stack
to a spectrum and step wedge. The
spectrum in this case is a color wheel
that represents the entire RGB spec-
trum through a range of luminosity
values, along with the grayscale step
wedge and some individual color
bars (see next page). There are lots
of ways to generate reference files,
and sometimes you’ll want to create
a specific set of swatches to check
the conversion, such as for adver-
tising to preserve a logo or product
color. For now, this test file will give
us a reasonable idea of whether
we missed anything in the original
Large stack of adjustment layers Original portrait