RawTherapee feature suggestion: cascading haldcluts in film simulation module

In the current RawTherapee 5.9, the film simulation module allows to pick a single HaldCLUT from a directory.
What would it take (from a development effort perspective, as well as from a resources usage perspective) to be able to cascade several HaldCLUTs instead?


Luts generally expect a well exposed, well defined input as they are basically a table of values…I am not sure that if you cascade them you could be guaranteed to get anything too useful or predictable… is there a use case for this??

I thought it would make sense to mimic (albeit in a limited way) what other apps do (i.e. be able to stack “filters”, as in “apply this velvia LUT and apply this monochrome LUT on top of it”).

LUTs will not do your color grading for you!.. this is a quote taken from here…

Getting a sense of what a LUT is and does might be the best answer to your query…

Thanks for sharing this article.

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If you want to see the effect, I believe you can use imagemagick and run multiple commands to apply multiple luts.

Suppose you have one image and two Hald cluts. You can apply the first clut, and apply the second clut to the result.

Or you could apply the second clut to the first clut. That makes a new clut. Then you can apply just that single new clut to the image. The result will be the same (assuming there is no clipping, and ignoring rounding errors).

Workaround: open photo, apply velvia lut, save as tiff, open that tiff and apply b&w lut.

I could have mentioned this workaround indeed :slight_smile: