disable camconst for DNG files?

Software
1

Is it possible to tell Rawtherapee to not use any predefined camera constants when opening DNG files?

Rawtherapee never opened the demosaiced-DNG files (linear DNG?) nicely that DxO Optics Pro / Photolab writes. It has a strong colorcast that you never quite can fix.

Recently Filmulator (which opened the DNG files just fine) made a change to use ‘camconst data from RT’, and suddenly the DNG files were starting to show the same problems.

After comparing looking at metadata and testing around, I noticed I can make RT to open the DNG files OK (or at least massively better) by using exiftool to write a BlackLevel metadata-header to ‘0 0 0’.

So, it’s only ‘annoying’ that I have to process the DNG files through another tool to make RT open them OK (while programs like Darktable, Filmulator, On1 PhotoRaw, ACDSee Photo Studio and more all open them fine. Heck, even dcraw works fine :)). But that annoyance is often enough for me to not try Rawtherapee anymore, which is a shame.

Is there an easy setting I can make somewhere to make Rawtherapee ignore the values in camconst.json when opening DNG files? Or opening the files while holding down a key or something.

2

If the data is already demoasiced, just write a tiff file from DxO and open that in RT, its most likely the same as what’s in the DNG.

On the other hand, you can write to DxO and tell them their DNG export is likely not writing files correctly.

3

If both the original dcraw and the libraw dcraw_emu, and also darktable read the file just fine, it’s something that Rawtherapee is doing.

Writing to DNG also enables most other programs to interpret the linear data and white balance and color-matrix like they will with the raw files. As in, writing to DNG allows me to actually use the look and processing (except demosaicing) of other programs. Darktable’s scene-referred color-calibration for example.

Disabling camconst for (linear) DNG files still seem like a normal thing to do. I think Rawtherapee uses the camconst data on DNG files to handle the raw data in it exactly the same as a normal RAW file would… but this is not applicable to linear DNG files I imagine.

4

@jorismak What happens if you open your original file in RT? Does it show up with proper black levels? If so, then I would hypothesize that DxO is rescaling the data when exporting to DNG. I’m not sure there is a failsafe way to detect this…

5

It’s a Linear DNG… it has no relation to the original RAW file :).

I just wish that Rawtherapee would not decide to interpret the DNG file in a special way.

Instead of assuming ‘blacklevel = 0’ because there is no blacklevel-metadata-information, it starts to take information from camconst.json, so it appears.

Let me ask the question another way:

Can I create a camconst.json next to my option file which ‘empties out’ certain camera models?

If I just make an empty entry with only the make_model, will it set the rest to defaults?

If not, what are the ‘defaults’ ? To reset entries.

6

This should be resolved in Filmulator already by doing exactly what you asked: disabling camconst for dngs. Is this not the case?

7

Yes it is!

Now I want the same in Rawtherapee :P.

I think I got the hang of modifying camconst.json in localappdata now, so I can disable the values for my camera models. I probably destroyed reading the normal raw files now, but I never do that any more to be honest.

8

FWIW, the DNG spec also says this should be the default case if the BlackLevel tag is absent.