There isn't an LUT tool in C*1, though it's on the feature list for v2. I can give a brief explanation of what an LUT is, though. If I'm explaining something you already know, sorry, but it seems like that's part of your question.
LUT stands for Look-Up Table. LUTs are color conversion setups from film to digital. The amount of color information in an 8-bit image is less than the amount of color information in a film frame (which is in turn less than the amount of color information in the visible spectrum, which is less than the amount of color information in the actual spectrum...).
So, if you just convert a film frame to an 8-bit digital image, it will change its appearance (for the worse) drastically. An LUT tells the program converting the image to use a different set of 256 colors per channel, rather than giving equal importance to the entire "regular" 8-bit spectrum (Linear color). The LUT itself is usually represented by a set of curves (or curves-slash-histogram) on a spectrum graph.
For instance, if you had a night scene in a film and were converting it to digital, your LUT would probably be a curve that's high in the "blue" and "dark" areas and lower in most of the others, and probably next to the bottom on the "light" areas. The 8-bit image that results will still only have 256 colors per channel, but it will be much closer to looking like the film image. If you were working with film you would likely be given LUT settings for the shots you are working on.
The extremely short explanation is that it's like setting up a custom palette for a GIF.
If anyone wants to correct or clarify any of that, feel free. I'm not an expert on it and may have been off on parts
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Brian Demong
Publisher, Combustion Instructor
Mesmer Animation Labs