To use dcamprof, you’ll need Argyll scanin to make the .ti3 file from the ColorChecker image
Of note, to use dcamprof you’ll need to compile it from source. Argyll is available already-compiled.
Argyll tools will get you a matrix profile, and is probably the most expedient alternative. dcamprof will do that, and it also has a number of options to do other things like make a gamut compression LUT from that data.
Edit: Geesh, I’ve spent too much time with these tools…
Let’s say I have a camera that has DNG+JPEG output support.
That camera has a JPEG mode that ALSO applies to video that has an unknown transfer function and unknown primaries.
I can use dcamprof to profile the DNG and create a DCP profile - but is there any tool that I can use to try and reverse engineer the primaries and transfer function of the JPEGs (which would also apply to video which cannot save raw/DNG data)
I suspect RT’s automatched tone curve would help with the transfer function reverse engineering - but is there any variation of AMTC that can use multiple images as a reference?
My issue is similar, there are a number of Action cameras and the like which have a wide colour gamut, high dynamic range mode and can capture JPEG or H.264. They use a proprietary transfer function and a primaries.
The Primaries don’t match any of the usual ones, 709, 2020, P3…
Once the primaries are known, I’m hoping to be able to write a nice tone mapper.
Yup, and unlike many of the “proprietary but targeted towards professional use” colorspaces (Sony S-Gamut, etc) and transfer functions (Canon C-Log, Sony S-Log1/2/3, Panasonic V-Log, etc) which have their primaries and transfer functions documented somewhere, many of these lower end cameras have arbitrary transfer functions and primaries that aren’t documented.
For example, the only documentation on Yuneec’s “FLAT” profile mode is “Intended for color grading in postprocessing” - HOW? To properly color grade this, I need to know the transfer function, and I need to know the primaries. Neither of these are documented ANYWHERE. The saturation/contrast properties of the video when displayed with something that assumes it’s Rec709 hint strongly that it’s a wide gamut log-transfer system, but you can’t properly generate a LUT for such a thing unless you know the actual primaries of the gamut and the transfer function.
All of the documentation I see regarding tiff transfer functions is related to an assumption that the tiff was saved with appropriate transfer function tags.
In this case, we have a JPEG that, in my case, has (at most) a manufacturer specific tag that says it was saved with the “FLAT” profile - which is undocumented and unknown.
What about Darktable chart. Create the lut and tone curve from the raw JPG pair. You could then apply that style to a haldclut PNG to make a lut as they do in raw therapies…might work??