At a minimum, as it was said, a proper color matrix would help.
Right now you are embedding an invalid one - there should not be any zeros in it.
After that, you could just embed D65 xy coordinates (0.31271, 0.32902)
in AsShotWhiteXY tag, and get a reasonable baseline white balance.
Any further calibration than that will have diminishing returns,
i don’t know about the convert to DNG part.
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@shyrodgau @LebedevRI Why not add the rudimentary support for the medium format back to rawspeed as well while at it?
Sounds like a good idea to me…
size: 15925248, w: 4608, h: 3456,
typ: 2,
size: 12937632, w: 4152, h: 3116,
typ: 3
size: 9806592, w: 3616, h: 2712,
typ: 3
size: 6470944, w: 2936, h: 2204,
typ: 3
size: 11943936, w: 3456, h: 3456,
typ: 4
size: 15335424, w: 4608, h: 3328,
typ: 1 (it is already there)
size: 11618752, w: 4012, h: 2896,
typ: 1
size: 7667520,w: 3260, h: 2352,
typ: 1
These are all currently confirmed possibilities (medium format has different sub-formats 6x4.5, 6x6 and 6x7 cm). For typ > 1 (Medium Format) the CFA filter array is line-swapped! plus there are some smaller formats configurable via an “Angle” Parameter, not all possibilities are known for the MF but probably will not occur in the wild very often (I would probably know if someone tried)
You’ll need to upload samples for all the sensors/raw outputs. I guess it can also wait if the products are not confirmed yet…
The products are all out, I just don’t have the samples, only most of the dimensions 
Can’t you ask the community for help?
Help from the community on color calibration would be more helpful… the DNG conversion itself can handle all formats and make the images available to a broader range of processor software.
I was thinking of asking the community for samples for raw.pixls.us, since you say you don’t have them.
Put up the question in the Users group, thanks! Also added 35mm angle medium from my collection. Angle small I can produce tomorrow.
First step is to get a calibration target that is supported by dcamprof - The X-Rite/Calibrite ColorChecker is the gold standard here. @kmilos already posted the link to RawTherapee’s color profiling document.
Per the linked article, you will need to shoot the target in direct noon sunlight, and also lit by a proper tungsten bulb (not fluorescent or LED, even a high-CRI one, although in the short term that’s better than nothing…) - the latter can be difficult in some countries. Tungsten bulbs are hard to find in the US, but they are still carried in Lowes or Home Depot if you spend a few minutes browsing the shelves. I bought a bulb and a bulb holder that I use only for profiling tasks.
If you encounter any issues with the process (especially if you have a fixed-lens fisheye camera but that does not seem to be the case here), we can help you if you encounter any snags - but the first step is to get a target.
I plan on updating that document later to hopefully resolve a few minor ambiguities, but right now there’s talk of replacing rawpedia with a different document management system - An update on Rawpedia
I’ve profiled multiple cameras (the included RawTherapee profiles for Sony A6300, A6500, and A7M4 were all either done by me or from test shots provided by me, and I also have a profile for the Xiaomi Mi Sphere 360 that many people have used) including fixed-lens fisheye cameras, so can help you with the details if you hit snags - but you need a target and appropriate light sources first!
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Thanks a lot! I rather meant our imback community to find someone who has access to a tungsten bulb and calibrate target. But more information is more helpful for me.
Tungsten calibration is optional (at least from darktable’s point of view). D65 (sunlight at noon) is the bare minimum for a single illuminant DNG/DCP profile as a starting point, and anyone has access to that. The color chart is, however, not optional 
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That looks rather old, so probably not. Also, unless you have a spectrophotometer, it needs to be supported by dcamprof.
More on that in this thread:
If you don’t want to break your head trying to figure it out, just get the ColorChecker Classic, the ColorChecker Classic Mini or the ColorChecker Passport 2. They are all supported by dcamprof with no further work needed.
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I have a copy of that book!
“Kodak Color Dataguide”, fifth edition, first printing, 1974. Bought it when I started to tinker with color darkroom stuff, did a couple of E-4 prints and just decided it was too much trouble for my paltry quantity of captures.
Looking at the patches, they could probably be measured and used to make passable matrix profiles. Really, all that’s needed are the red, green, and blue patches along with absolute white and black.
Hmmm. All this turns out to be close to an overkill for the thing we try to do… the ImBack is not supposed to be a high quality digital camera replacement (there are too many physical and optical flaws in the whole system -it is to produce ART rather). Just the fact that the JPEG processor included in the product more resembles a mobile phone and does a lot of things that makes some people want to shoot raw) - is it worth what I am asking at all?
Well, there’s a certain amount of investment required to do the basic thing…
The ColorChecker Passport won’t be a “one-trick pony” acquisition. Just having the neutral card and patches makes it suitable for in-scene white balance measurements, and the color target can be used for “normalizing” other cameras recording a scene against a reference camera. That’s in addition to allowing you to make camera profiles with abandon.
My feeling about “art” is that it also requires some adherence to colorimetry to make the basis for aesthetic departure. FWIW…
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Surely there is someone in Frankfurt or Germany that can loan you a color checker, or you can probably rent one.
True, D65 is the bare minimum. This is one of the few cases where I’m spoiled by living in an environmentally backwards country - while the US is also aggressively pushing CFL/LED, they are not doing so nearly as heavily as Europe so you can still find and buy regular tungsten bulbs not marked as “speciality” (albeit we’re at least doing well enough that you need to spend some time searching the shelves because there are maybe 2-3 regular tunsten products among multiple large shelves of CFL and LED products).
I also agree with @ggbutcher - the Passport Photo 2 is a damn good white balance and exposure reference. I use it for color calibration maybe 1-2 times a year at most, but use the white balance and grey card parts of it on a regular basis. (That said, on my most recent vacation, I found the need for a waterproof alternative that I did not have.)
It’s not that expensive and I’ve found it to be worth every penny.