Dng4ps: wrong white balance, in camera dng: right white balance - RAW Shooting and Processing - CHDK Forum
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Dng4ps: wrong white balance, in camera dng: right white balance

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Offline Fytrius

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Dng4ps: wrong white balance, in camera dng: right white balance
« on: 13 / May / 2009, 17:38:16 »
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Hello!

I've come to the conclusion that Raw Therapee can't open a dng made by dng4ps with correct white balance ("Camera" or "As Shot" option selected of course). In fact; it doesn't matter how you have set the camera white balance; Raw Therapee always opens an image with the same value in white balance - never corresponding to the jpg image from the camera. This also counts for Lightroom, CS4, picasa etc. The only application so far opening a dng from dng4ps correct is Irfanview.

But if I choose in camera dng "conversion" (A720IS) it suddenly gets alright. Raw Therapee then produces a result corresponding to the jpg image.

So what is wrong in this picture?  :D

It is obvious that a dng produced by dng4ps has white balance information since Irfanview can find it, but what about Raw Therapee and the others? Is it dng4ps "fault"? Have I missed something?

The reason I ask is that it is easier transferring the pictures in crw-format with "Canon camera window" than removing the memory card for accessing the dng. I usually don't transfer many pictures each time....

« Last Edit: 13 / May / 2009, 17:54:33 by Fytrius »
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Offline vit40

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Re: Dng4ps: wrong white balance, in camera dng: right white balance
« Reply #1 on: 14 / May / 2009, 03:56:44 »
dng produced by dng4ps/dng4ps2 has no white balance information. It has exif information from corresponding jpeg, which doesn't have WB information

dng produced by the camera has WB info, because Ewavr found a way to read it from the camera (if I remembered correctly), and write it to a dng
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Offline Fytrius

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Re: Dng4ps: wrong white balance, in camera dng: right white balance
« Reply #2 on: 14 / May / 2009, 06:14:57 »
Can you then explain why Irfanview displays dng:s from dng4ps correct but not the others?

AND...if I use dng:s produced by the camera Irfanview NO LONGER displays the image correct but Raw Therapee, Lightroom etc start doing it??

It seems to me that even dng:s from dng4ps holds white balance information but in a "different location" in the file so that Raw Therapee can't use it.
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Offline vit40

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Re: Dng4ps: wrong white balance, in camera dng: right white balance
« Reply #3 on: 14 / May / 2009, 12:41:51 »
Well, can't say why Irfan displays image correctly, I only know that it's using dcraw as raw developing engine and that there is a checkbox "use camera whhite balance, if possible" in properties enu

But there is no such information in a dng produced by dng4ps. Raw file from camera is only a memory dump with no other info, dng4ps only repacks this to a dng format and appends exif information from a jpg file. Jpg from canon compact cameras has no WB info (unlike jpg from Canon DSLR, which has complete WB info) - it can be veryfied with some utility like exiftool, which display all exif tags in jpg, inlcuding undocumented maker notes
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Offline Fytrius

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Re: Dng4ps: wrong white balance, in camera dng: right white balance
« Reply #4 on: 14 / May / 2009, 15:03:36 »
I found the solution thanks to your comments vit40!

I wasn't looking at a dng with the same white balance as corresponding jpg in Irfanview - I was in fact looking at exactly the same picture!

Dng4ps embed the jpg in full size (default) in the dng for faster preview. Irfanview has an option under plugins tab called "Try to load embedded preview image (if available)". Unchecking this confirmed what you said: no white balance information in the dng.

No wonder i got "fooled"...

Thanks!
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Offline user1

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Re: Dng4ps: wrong white balance, in camera dng: right white balance
« Reply #5 on: 14 / May / 2009, 15:27:51 »
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Offline vit40

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Re: Dng4ps: wrong white balance, in camera dng: right white balance
« Reply #6 on: 14 / May / 2009, 17:45:26 »
Huh - obviously I didn't follow that thread to the end

So, exiftool doesn't know about this maker note content (it's filled with zeros in jpgs produced by 400D for example - WB infos are in other maker notes). So, it would be possible to write a small utility to read WB info from jpg and write it to a dng, made by dng4ps, is someone preffers this workflow instead of using dng produced by CHDK, like me, as writing of dng in camera is slower. I don't need it anyway, because WB measured by the camera usually isn't good enough for me, so I preffer to set WB manually even during developing raw files from my 400D, which have AWB info inside
« Last Edit: 14 / May / 2009, 17:47:25 by vit40 »
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