Colour Calibration module — DNG

From the new DT manual: “ DNG RAW files are also ignored since they can (but don’t have to) interpolate between 2 embedded DNG profiles to perform white balancing, which can affect the settings. For these cases, you will have to configure the settings yourself and use your camera manufacturer’s documentation to take the appropriate color correction steps.” Link

I use Adobe DNG Converter to convert my camera raw files to DNG. Does the above comment apply to my situation?

Am I reading the manual’s quote correctly? Does it mean that I will get better results from DT if I stop using Adobe DNG Converter on my files?

Cheers

If dt can handle the format, why don’t you try it yourself? If dt can’t handle your raw files, what other option do you have (assuming you want to use dt)

For the rest, it’s impossible to answer, as you don’t mention what camera you are using to produce the raw files.

Hmm, I thought the interpolation between the embedded profiles was to come up with a temperature-specific color primary set, but white balance was still separate. @T_N_Args, not a question to you, but to others that know DT guts and/or DNG guts…

DNG is a file format that can represent anything, from a mosaiced RAW to a non-mosaiced arbitrary raster (scan, pre-demosaiced RAW, etc.), including “not-so-RAW-anymore” raster images with color profiles and white balance already applied, and can ship vanilla color profiles (white-balance independent) as well as color profiles that already contain the WB correction built-in (which is the essence of the DNG profiles interpolation).

People should really stop using that shit and expecting us to handle any possible combinations of sub-cases of Adobe’s mess.

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That’s a fair point, but for some of us who use cameras with unsupported formats such as the Canon CR3 don’t have much choice if we want to stay with a raw format. Not a complaint with the CR3 status with Darktable, it’s just the reality of the situation

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If you merely convert file formats, you should have an option somewhere to let everything as-is, except for the file container, it’s your responsibility to check that the software does not get clever.

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Thanks, that’s good to know. Personally, I’m considering a Canon upgrade sometime this summer and my ability to continue using DT is a limiting factor, and for now it would seem that CR3 > DNG conversion seems to be the only reasonable workaround.

There’s a good chance to have native cr3 support in summer since there’s a „task force“ working on this at exiv2

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Thanks. I am using it to “merely convert file formats” – all I want to do is losslessly compress the giant 84 MB raw files from my Sony A7R3. If the camera supported lossless compression, I wouldn’t use Adobe DNG Converter at all, but the only options Sony give me are 84 MB or lossy compression. The Converter gets my 84 MB ARW files down to 40-ish MB lossless.

Here is the user interface and preferences panel for Adobe DNG Converter. Showing the preferences I use. I don’t even see any options that allow me to “make sure it doesn’t get clever”.

Until I noticed the text (from DT 3.4 Manual) that I started this thread with, I was not seeing any issues with using my DNG files on DT. However, I had not been paying attention to the new Color Calibration module, until I started reading about it to try and learn it.

My purpose in starting this thread is to learn whether my DNG raw files are being “ignored” by the Color Calibration module. Is there a clue in the module’s settings that tells me whether it is being “ignored”? Will it be blindingly obvious from a glance at the image if it is being “ignored”, or is it subtle?

Sample DNG image (if it helps): _A7R0544.dng (43.5 MB)

thanks (L-plate attached)

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This is what I get when simply opening your pic in dt master. Is that not correct ?

Not a problem for me, darktable 3.4.1.1
_A7R0544.dng.xmp (10,0 Ko)

It looks correct to me.

So, are you saying that there is no problem if the Color Calibration module opens on my DNG file?

What would you see when you opened my file if there was an issue?

I started this thread because I was concerned, by the DT manual’s warning about DNG files, “DNG RAW files are also ignored…”, that there might be something subtle and difficult to detect going wrong with my DNG file colours in DT using the Color Calibration module, and I am asking how do I spot when this problem is happening.

If you are saying “your DNG file opens in DT, Color Calibration module opens in DT, no problem”, then that is good to know, and simple to check.

Cheers

If you can follow the math here…
https://www.odelama.com/photo/Developing-a-RAW-Photo-by-hand/Developing-a-RAW-Photo-by-hand_Part-2/#usingcolormatricesfromadobedng

.I might take a stab at it you could calculate what your WB values should be here for D65 and see if DT is using those. If so then the CC module should be accurate…

If not I guess you could create a preset with the right D65 coefficients and use that???

image

So I just took a raw file. RW2 and converted it to DNG. It was a colorchecker. I tried all 3 WB modes and recorded the RGB coefficients. So as shot, camera reference and spot WB on the white patch of the colorchecker. Then I repeated the same on the DNG file. The coefficients were the same for eaqch method of WB. Then switching to modern wb workflow and resetting the stack gave the same values in the color calibration module for each file as well. The rgb values of the white patch were also the same between DNG and the RW2 file. So for this file there was no apparent difference using the calibration mode on the raw or dng…There is a difference in the ultimate WB. The closest comparison I could make was spot WB vs CC selecting the white patch. The temp values are not comparable and wouldn’t be with color calibration but the white patch values were 129 129 129 for the Spot WB and 137 132 141 for the color calibration method selecting the white patch for a neutral reference. So there is a difference from what I could see between the methods but not between DNG and the original raw. I could test a few more files but this is what I observed…

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Took a quick look at this and this should ensure CC works I think as a spin off of fixing this issue…

Thanks Todd, appreciate your effort looking into this. “No difference between DNG and the original raw” is good news for me.