Issues with creating LUTs in RawTherapee

Processing
1

I wonder if this is me making an error or something I’ve missed.
I am working on creating a Kodachrome 64 Generic (from the RawTherapee CLUTs) lookalike and then saving it as a CLUT itself. The issue is that once exported as a CLUT I get slightly different colours. In the screenshots I converted the raw into a TIFF but it’s too large so I am uploading the RAW.

Screenshot from 2025-06-30 13-44-05
Screenshot from 2025-06-30 13-44-051600×900 731 KB

Screenshot from 2025-06-30 13-44-09
Screenshot from 2025-06-30 13-44-091600×900 730 KB

MCCURRY-2025-3-good-generic64-A7206978.ARW.pp3 (16.2 KB)
A7206978.ARW (46.9 MB)

2

What’s your process for creating the CLUTs?

1 Like
3

I create an edit working on a TIFF version of the RAW file. Then I open the LUT identity TIFF file and apply the same edit to it, then save it. Using the resulting file should give the same colours as the RawTherapee edit …according to my understanding.

4

also thanks for responding :slight_smile:

5

I get almost identical results applying the pp3 vs the CLUT created from the pp3. Here’s what I did.

  1. Convert the raw into a 16-bit float tiff with the neutral profile.
  2. Apply the pp3 to a level 12 (1728x1728 pixels) identity HaldCLUT. Save it as an 8-bit png with an sRGB output profile.
  3. Apply the pp3 to the tiff. Take a snapshot. Reset and apply the HaldCLUT. Take a snapshot.

pp3:

pp3
pp31600×900 218 KB

HaldCLUT:

HaldCLUT
HaldCLUT1600×900 219 KB

I also tried it on a tiff created by applying the auto-matched tone curve profile to get a similar starting point as what you show in your screenshots. There were slight differences, but not as noticeable as your examples.

I noticed the pp3 is using the tone equalizer, which tries to preserve local contrast. You should reduce the regularization to the minimum value or use a different tool to adjust the tones. I got even closer (nearly identical) results:

pp3:

PP3 Improved
PP3 Improved1600×900 216 KB

HaldCLUT:

HaldCLUT Improved
HaldCLUT Improved1600×900 216 KB

1 Like
6

Thank you so much for taking the time to respond. Could you upload the proper “neutral” identity file so I can use it going forward, I feel like when I create them something goes weird. Also the pp3 for the preset when applying it to the identity so I can have the output profile right as well?

Either way this is great, thank you!

7

You can get the identity HaldCLUT from here: File:Hald CLUT Identity.tif - RawPedia
I didn’t adjust the output color profile from your pp3. I only reduced the Tone Equalizer regularization.