Color Grading LUT's

Processing
1

Hi!

Do you all ever use 3D LUT’s for color grading still pictures ?
(There are gazillions of free LUT files to download over the web.)
Do you think this is a useful tool ?
If so, what is your favorite format ? *.cube maybe ?

I am not 100 % sure just about which format to pick to support in my raw processing code…

Thanks!
L.

2

Its about much more than just picking a lut and a lut format…the LUT expects well exposed input in general and its a table to map pixels. When it is created it maps pixels in one space often to another …so you need to be able to match that in the DT lut module and it has limited support…

You can of course still use them but they could generate a result nothing like what you expect and also you can introduce clipping and banding if you are not careful…but experiment and see what you find…

THere are different types of luts…look vs technical vs hybrid and likely some others…

Here is a quick cheat sheet…

3

I sometimes use LUTs, either

  1. When I see what I can do with the picture right away and I know I have some LUT for that purpose
  2. When I don’t really know what to do with the colors anymore, so I just try stuff and see if something sticks…

I mostly use film sim LUTs from the RT wiki page (.png), but I sometimes use .cube downloaded from random places as well. A few years ago I’ve made some myself by reverse engineering filters in my phone editing app by applying the effect on an identity LUT .png. And lastly, I tend to combine LUTs with some overlay effects like average and decrease opacity if the effect is too strong.

4

The cube format has been pretty universal but suffers from a lack of a properly defined header.

They’re usually used in video and lack any information on the input and output colour space, the range over which they’re expected to apply etc. The user needs to know what parameters the LUT processor requires. This is less of an issue with stills, but still a problem.

AMPAS initially and now SMPTE are working on the Common LUT Format which addresses all of these issues with LUTs