[Bug 142055] New: Which whitebalance is used

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           Summary: Which whitebalance is used
           Product: digikam
           Version: 0.9.0
          Platform: SuSE RPMs
        OS/Version: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: NOR
         Component: general
        AssignedTo: digikam-devel kde org
        ReportedBy: peter.mueller_1955 yahoo com


Version:           0.9.0 (using KDE KDE 3.5.6)
Installed from:    SuSE RPMs
OS:                Linux

Somehow I don't trust the whitebalance dialog in digikam. First of all it displays a value different from other program - I shoot in raw using a Canon 300D. If I change the value to the value other programs show (e.g. bibble) the picture is too warm. Secondly what confuses me is that you can change the white balance of a jpeg  picture and not only raw.

What is behind your white balance function?

Somehow I have the feeling that you transform the raw picture to a jpeg and then do some changes to the jpeg. Changes like white balance, saturation, etc. Here you calculate the change but they are not as good as if you would do it to the raw picture. What do you do actually?
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[Gilles Caulier-4]

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------- Additional Comments From caulier.gilles gmail com  2007-02-22 14:53 -------
>Somehow I have the feeling that you transform the raw picture to a jpeg and >then do some changes to the jpeg

Certainly not. All pixels value are store in memory in 16 bits. the algorithm process WB change with this color depth.

The difference are duing to different algorithm used by other programs. In digiKam this algorithm come from the old RawPhoto gimp plugin (initialy only 8 bits support)

http://wolf.ifj.edu.pl/~jochym/soft.php

Gilles Caulier
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[Gilles Caulier-4]

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           What    |Removed                     |Added
----------------------------------------------------------------------------
            Product|digikam                     |digikamimageplugins
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[Gilles Caulier-4]

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           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|general                     |White Balance
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------- Additional Comments From peter.mueller_1955 yahoo com  2007-02-22 15:10 -------
Two more questions:

1. How do you change the white balance of a jpeg?

2. 5000K is 5000K, why should I see "different" pictures using different programs? (on the same LCD of course)
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------- Additional Comments From casta xwing info  2007-08-25 19:33 -------
Hi

Peter, I think you are confusing RAW white balance and RGB white balance.
Currently, the digiKam "White Balance" acts on the RGB space, so AFTER raw conversion.
So in fact, temperature provided within the WB tool is relative to the original WB of the picture (which is not necessary neutral). So there is a biais in temperature interpretation in this tool.

Currently, white balance during RAW conversion is only handeled for automatic and camera embeded white balance (in dcraw setup in digiKam configuration box).

By the way, I agree that the values are quite strange. Having a "Neutral" WB (that provides RGB multipliers = (1, 1, 1)) at 4750K and 1.2 green multiplier sounds quite strange to me.
IMHO it would be far less strange to have the neutral point at standard CIE D65 with 1.0 green multiplier...

To change that, here[1] is a proposal to change the way of calculating the RGB multipliers from the pair (temperature, green multiplier). I have ported the algorithm from ufraw, that set the neutral white point at D65 illumination. That sounds to me far much logical since it's a widely spread standard.
Moreover, it does not need anymore the enormous blackbody.h matrix.
At your appreciation, but I think it could be a good thing to apply to digiKam ;)

[1] http://casta.nerim.net/digiKam/digikam-kde3-WB-ufraw-multiplier.patch

Regards
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------- Additional Comments From caulier.gilles gmail com  2007-08-26 13:04 -------
Guillaume,

Thanks for the patch. I will test it.

What's about to adjust automaticly the dcraw WB settings during RAW decoding, especially in 16 bits mode ?

To digiKam users : Please test this patch against KDE3 branch of digiKam svn repository, and give me if all is fine for you to adjust WB of your pictures.

Gilles
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------- Additional Comments From casta xwing info  2007-08-26 13:24 -------
> What's about to adjust automaticly the dcraw WB settings during RAW decoding, especially in 16 bits mode ?

I have a working solution about a more flexible WB adjustment during raw decoding (in fact, the current version is here[1], based on ufraw WB to RGB multipliers conversion : ) ;)
Especially within kipi-plugin rawconverter, it makes WB correction very handy, the only missing feature is the color picker to automaticaly neutralize...

But before sending it "officially", I must know if you want to keep the current digiKam algorithm or if you will apply my patch to use ufraw way of converting temperature to RGB multipliers : the WB computation of the RGB multipliers should be the same on both side to be more coherent :)

[1] http://casta.nerim.net/digiKam/libkdcraw-kde3-dcraw-WB.patch
http://casta.nerim.net/digiKam/digikam-kde3-dcraw-WB.patch
http://casta.nerim.net/digiKam/kipi-plugins-kde3-dcraw-WB.patch

Regards

PS: sorry for not providing also the kde4 branch patch : my kde4 digiKam version compiles but does not currently starts, so I cannot test anything...
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------- Additional Comments From casta xwing info  2007-09-02 21:21 -------
Here is the same patch for the kde4 branch (I finally set up a correct kde4 env to test it) :
http://casta.nerim.net/digiKam/digikam-kde4-WB-ufraw-multiplier.patch

Guillaume
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------- Additional Comments From caulier.gilles gmail com  2007-09-03 14:15 -------
Guillaume,

KDE3 patches sound good for me. I will apply it on svn later than libkdcraw 0.1.2 will be release to not broke release plan planed by Angelo.

Your KDE4 patch is completely different. Its about white balance image editor plugin... Why ?

Gilles
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                 CC|                            |jgoerzen complete org



------- Additional Comments From caulier.gilles gmail com  2007-09-03 14:20 -------
*** Bug 148561 has been marked as a duplicate of this bug. ***
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------- Additional Comments From casta xwing info  2007-09-03 19:16 -------
the kde4 patch at comment #6 is relative to the same patch for kde3 branch at comment #3 ;)

The patches for kde4 branch of libkdcraw I spoke about at #5 comment are here :
http://casta.nerim.net/digiKam/digikam-kde4-dcraw-WB.patch
http://casta.nerim.net/digiKam/libkdcraw-kde4-dcraw-WB.patch
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           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|White Balance               |libkdcraw
            Product|digikamimageplugins         |kipiplugins
            Version|0.9.0                       |unspecified
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           What    |Removed                     |Added
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         AssignedTo|digikam-devel kde org       |kde-imaging kde org
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