Color checker bar matching

[JCB Webb]

Greetings! I am an intern in the cultural heritage sector and need to color correct photos with a Kodak color checker reference bar in the frame. For a short term fix I used Levels to improve some of the images. For the long term I would like to learn the right way to use the color info in the color reference bar to do systematic color correction in GIMP. 

I did web and forum searches with permutations of "color checker" "color reference" etc, but couldn't find any GIMP tutorials. I know how to do this in Photoshop, but I prefer to do as much graphics work as possible in GIMP. Thank you for your assistance!

- JCB

[Ofnuts]

A very good script is Luca de Alfaro's white-balance. Basically, you would use the color picker to set the foreground color from one of the middle-gray squares in your checker, and then call the script, that does the appropriate color changes to make that color gray (R=G=B). Note that this doesn't attempt to fix exposure.

If you want more accurate results, 1) you use a camera that has a "raw" mode (so you have more dynamic range) and 2) you use a de-mosaicing application. There are many such free apps, many of these are discussed/supported here.