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Bug #12027

automatic color balance isn't working with input icc profile

Added by Nicolas Houdelot 8 months ago. Updated 8 months ago.

Status:
New
Priority:
Low
Assignee:
-
Category:
Darkroom
Target version:
-
Start date:
02/22/2018
Due date:
% Done:

0%

Affected Version:
2.4.1
System:
Ubuntu
bitness:
64-bit
hardware architecture:
amd64/x86

Description

hello,
I'm using white balance for a long time, it it seems to work very good.
but everytime I was using it, it was with a picture that has an embeded color profile.

but now for slide i'm using a different process, where at first, I select an input profile in darktable.
then do the usual automatic enhance process, and finish with white balance, and exposure.

the problem is that white balance isn't working in this process.
i mean... eveytime i'm trying to use the automatic "spot" option, it never white balance on white, but on another color
it's like it's trying to white balance without the input profile i selected
and so.. the white is not white.

exemple_prophoto.png - RAW -> v700 profile -> ProphotoRGB (3.71 MB) Nicolas Houdelot, 02/22/2018 04:28 PM

exemple_v700.png - RAW -> v700 profile (3.19 MB) Nicolas Houdelot, 02/22/2018 04:28 PM

exemple_prophoto_notkodak.png (3.69 MB) Nicolas Houdelot, 03/02/2018 07:16 PM

History

#1 Updated by Roman Lebedev 8 months ago

Nicolas Houdelot wrote:

hello,
I'm using white balance for a long time, it it seems to work very good.
but everytime I was using it, it was with a picture that has an embeded color profile.

but now for slide i'm using a different process, where at first, I select an input profile in darktable.
then do the usual automatic enhance process, and finish with white balance, and exposure.

the problem is that white balance isn't working in this process.
i mean... eveytime i'm trying to use the automatic "spot" option, it never white balance on white, but on another color
it's like it's trying to white balance without the input profile i selected
and so.. the white is not white.

That makes no sense, https://www.darktable.org/usermanual/en/darkroom_concepts.html#pixelpipe

#2 Updated by Nicolas Houdelot 8 months ago

Roman Lebedev wrote:

Nicolas Houdelot wrote:

hello,
I'm using white balance for a long time, it it seems to work very good.
but everytime I was using it, it was with a picture that has an embeded color profile.

but now for slide i'm using a different process, where at first, I select an input profile in darktable.
then do the usual automatic enhance process, and finish with white balance, and exposure.

the problem is that white balance isn't working in this process.
i mean... eveytime i'm trying to use the automatic "spot" option, it never white balance on white, but on another color
it's like it's trying to white balance without the input profile i selected
and so.. the white is not white.

That makes no sense, https://www.darktable.org/usermanual/en/darkroom_concepts.html#pixelpipe

I understand that the history stack, does not reflect the actual order of the process.
the files i'm using are raw files (gamma 1) generated by vuescan.
I apply a profile (generated using an IT8 Target) to get the correct color values

anyway, i did more tests, i was wrong about what was happening.
in fact here are 2 slides scans, converted from RAW using photoshop

one from RAW -> v700 profile -> ProphotoRGB
the other RAW -> v700 profile

if I open them on Darktable, they display correctly
but if a do an auto white balance on it (using spot), I get different results.
that's what I don't understand

#3 Updated by Tobias Ellinghaus 8 months ago

White balance is applied before input color profile. So it makes sense that the result differs.

#4 Updated by Nicolas Houdelot 8 months ago

Tobias Ellinghaus wrote:

White balance is applied before input color profile. So it makes sense that the result differs.

ok, it make sense, because it's working this way.

but the problem is... a user should do an automatic white balance whatever the profile is.
it doesn't seems a good thing, that this function is working only with pictures with some icc profiles.
that's unexpected.
and i don't see a workaround except to convert all pictures using a working well profile with auto white balance.

I don't want to ask you to change the order of the process. perhaps this can be solved by correcting the value of the spot function given to the module ? i don't know.

#5 Updated by Tobias Ellinghaus 8 months ago

I just tried with some test pictures using sRGB and AdobeRGB profiles. Those behaved identical when using spot white balance. Maybe the real problem is the color profile you are using?

#6 Updated by Nicolas Houdelot 8 months ago

Both of them have a white point at 6500K
not for my profile who has a white point at 6700K

I did further investigations, I also tried a picture with the new Rec2020 color profile, and there's a little difference, but not so much.

I tried something similar in photoshop with "automatic colors".
by loading the pictures, and not converting them to the working profile (ProPhotoRGB),
that way i keep them to their original profile. I also get different results..
so, perhaps it's normal, due to the algorithm used to white balance pictures

it's a little annoying cause i never though there would be a difference.
in fact, in photoshop, with the notion of "working icc profile", you avoid to have different results.
(once you use a profile that is proof to work correctly with this tool)

as it doesn't exist in darktable, i guess i should add another process to my scanning procedure, and manually convert pictures to my usual working profile.

I would prefer to have a working profile notion in darktable as well.. but it's kind of a change.
And i'm not sure it's one of the reasons it exists.

anyway. my conclusion is that automatic color balance will never give you the same result, whatever the profile is. It might be the way things are. The workaround is to open pictures with a profile that is "proof to work" with this tool.

if you don't see anything else, i guess you can close this bug.

#7 Updated by Tobias Ellinghaus 8 months ago

One thing I see with you images is that libpng is complaining about the ProPhoto profile embedded in the one file is broken:

libpng warning: iCCP: profile 'Photoshop ICC profile': 0h: PCS illuminant is not D50

Where did you get that profile from?

#8 Updated by Nicolas Houdelot 8 months ago

huum...
in fact there's one in /usr/share/color/icc/colord/ (13 kb)
but it is not branded Kodak, unlike the one i've send

to make this exemple, i used photoshop CS2 with wine.
it seems that there's a ProPhotoRGB embeded with photoshop (i can't find one in windows/system32/spool/drivers/color/)
if i save a picture, his profile is Kodak branded
if i add the ProPhotoRGB from /usr/share/color/icc/colord/ to windows/system32/spool/drivers/color/
and save a picture, his profile is not Kodak branded anymore.
in the color preferences of photoshop, the ProPhotoRGB profile moved from the previous section (the embeded one ?) to the other (with my added profile)

it seems that there also a profile in my ~/.local/share/icc/ (940 bytes) who is Branded "Kodak"
i deleted it.
thanks for seeing this, I had problems with digikam, while converting pictures, perhaps it's the cause.
I don't think that will change anything, except for digikam (i was only using it as an output profile in darktable)

here is the prophoto exemple, with the 13 kb profile

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