Inspiring

Question

Color Lookup Tables

Forum|Forum|4 years ago
August 3, 2021
3 replies
6448 views

Can anyone point me toward more detailed information about creating color lookup tables? I get a "Could not export Color Lookup Tables because this document has no adjustment layers" error message when I try to create one using File/Export/Color Lookup Tables. I don't have any adjustment layers because I just have a page with a color palette on it. I tried adding a Brightness/Contrast adjustment layer (without actually making any changes to those settings) and didn't get the error message again. However, when I tried to use the resulting LUT, it doesn't appear to do anything unless I change the Data Order from RGB to BGR. Unfortunately, that does about the opposite of what I was hoping for.

Windows

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davescm

Community Expert

What exactly are you trying to achieve with a Look up Table? It may be you are using the wrong function.

A look up table attempts to simulate the changes made by a variety of adjustment layers by making a table which acts on the pixels in a new image in a similar way to the combination of adjustment layers in the original. So, for example, if you had an adjustment layer which increased contrast and another adjustment layer that shifted everything toward blue - then the resulting LUT would make a similar adjustment on other images.

Dave

scotwllmAuthor

Inspiring

What I’m trying to do is apply seasonal color palettes to photos. If the skin of the photo’s subject is lighter and warmer than average, then I’d use the spring palette. If they’re lighter and cooler than average, they get the Summer palette. If they’re darker and warmer, they get the Autumn palette, and if they’re darker and cooler, they get the Winter palette. I figured Photoshop would lookup the colors in the photo in a table that remaps it to another color. “OK. All you orange pixels are now blue.”

T

Test Screen Name

Legend

Well, you're absolutely right. A colour lookup table is used to transform colours. It's a list of the colours be used to transform. But it's also much more complicated than you put it. What is "orange"? Many thousands of colours are orange. A look up table has to be able to transform ALL POSSIBLE colours. How many is that? For an 8-bit image it's 8 x 8 x 8 which is just under 17 million. So a lookup table needs to (sorta) list what colour you want to get from each of those 17 million colours. It could list 17 million colour values, which would take about 48 megabytes. In fact a look up table is smaller than that but it often has tens of thousands of colours, and expects Photoshop to work out the values in between by maths (lots of it).

There are many tools and ways to make a lookup table. In Photoshop it builds on the fact that Photoshop already has lots of tools to transform colour. Like, the brightness/contrast settings. Adjusting curves. And many more. You can save the settings as a LUT (look up table file) for two reasons

* to save your carefully worked out adjustments to use again in Photoshop

* to let other apps do those clever things Photoshop can do (especially for videos, frame by frame).

I'm not quite sure what you can do with a palette such as you describe. Is it systematic - specific RGB values for each of a systematic range of input RGB values? Or is it more a guide for a skilled artist to use? If you can say what you have, someone here (not me) may have an idea of how you can either turn it into an LUT, or otherwise use it. Or maybe what you need to do is look at established LUTs for sale - there are many thousands and it could be a huge time-saver for you.

T

Test Screen Name

Legend

The adjustment layer has to do all the work. It sounds as if you've added an adjustment layer for brightness, without changing brightness - which does nothing. The colour palette that you have in a page doesn't seem to have anything to do with making a colour lookup table.

I wonder if this is helpful: https://www.youtube.com/watch?v=FFPcqIrY2YQ

scotwllmAuthor

Inspiring

The video is very helpful. The narrator mentions a bunch of rules and ‘how to’ steps. Where are they documented?

I think part of the problem I’m having is that “color lookup table” does not appear to have anything to do with looking up colors in a table.

What I’m trying to do is apply seasonal color palettes to photos. If the skin of the photo’s subject is lighter and warmer than average, then I’d use the spring palette. If they’re lighter and cooler than average, they get the Summer palette. If they’re darker and warmer, they get the Autumn palette, and if they’re darker and cooler, they get the Winter palette. I figured Photoshop would lookup the colors in the photo in a table that remaps it to another color. “OK. All you orange pixels are now blue.”

Scott

c.pfaffenbichler

Community Expert

»I don't have any adjustment layers because I just have a page with a color palette on it.«

Then there is no data that Photoshop can use to create a LUT.

Quote from

https://helpx.adobe.com/photoshop/using/export-color-lookup-tables.html

»You can export color lookup tables only from documents that have a background layer and additional layers to modify colors.«

scotwllmAuthor

Inspiring

That answer is not helpful as the initial question was "Can anyone point me toward more detailed information about creating color lookup tables?"

c.pfaffenbichler

Community Expert

@scotwllm wrote:

That answer is not helpful as the initial question was "Can anyone point me toward more detailed information about creating color lookup tables?"

Have you read the page I posted a link to before posting that?

If you want to create LUTs outside of Photoshop then you may also want to search elsewhere than on a Photoshop Forum, but in Photoshop LUTS cannot be created based on a pixel Layer but based on Adjustment Layers.

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