Some color management questions

[krienke]

Hello,

i run digikam 0.10 on my openSuSE 11.1 box. All my photos are in sRGB
colorspace. JPG files I convert from my cameras NEF files (using bibble) are
also in sRGB. In digikam colormanagement is disabled. So far so good. Up to
now I never had any color problems.

Today a friend send me some JPG photos. I know he also shoots in RAW (Nikon
D300) and then converts these files into either tiff or JPG. We spent a
holiday together and now exchanged some photos, he sent me JPG files. He is
working with windows, I guess to remember he is using Nikon Capture and Adobe
Photoshop to process his photos.

When I saw his photos and compared them to mine the first thing that I saw,
was that color saturation in all of his photos looks to me rather small. Some
photos actually look a little pastel-colored and there is some yellow tint in
quite all of his photos. Color is not completely wrong but looks in my eyes  a
little strange.

I looked at the photos XMP metadata where I found a Photoshop section. In this
section there is an entry "ICCProfile" with a value of "Adobe RGB (1998)".

- Does this mean that color in these JPGs is in Adobe RGB 1998 and not in
sRGB? If yes then perhaps this difference in colorspace could be the reason
for the pale colors, couldn't it?

- What should digikam actually do with a photo that is in Adobe RGB color
space?  Would it be automatically convert it to sRGB when I look at it? Do I
have to activate colormanagement in digikam to get things right even if I just
want to look at these photos?

- Can a JPG actually contain an image in Adobe RGB or is (or should be) the
colorspace by definition sRGB in all JPGs?

I am actually unsure if I really have a color problem or if everything is the
way it should be, but since my friend does not live next door I cannot just
take a look on his monitor to see if he intended this "special" color look.

Thanks for your help
Rainer

--
Rainer Krienke, Uni Koblenz, Rechenzentrum, A22, Universitaetsstrasse  1
56070 Koblenz, http://www.uni-koblenz.de/~krienke, Tel: [phone]
PGP: http://www.uni-koblenz.de/~krienke/mypgp.html,Fax: [phone]

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[Gys van Zyl]

I don't use the color management features of digiKam, so I can't give you any guidance there.  What you can do is to open one of his jpegs in Gimp and choose to convert to sRGB when Gimp prompts to do so.  You will then have a better idea of what your friend intended the photo to look like.

On Sat, Jun 13, 2009 at 2:35 PM, Rainer Krienke <[hidden email]> wrote:

Hello,

i run digikam 0.10 on my openSuSE 11.1 box. All my photos are in sRGB
colorspace. JPG files I convert from my cameras NEF files (using bibble) are
also in sRGB. In digikam colormanagement is disabled. So far so good. Up to
now I never had any color problems.

Today a friend send me some JPG photos. I know he also shoots in RAW (Nikon
D300) and then converts these files into either tiff or JPG. We spent a
holiday together and now exchanged some photos, he sent me JPG files. He is
working with windows, I guess to remember he is using Nikon Capture and Adobe
Photoshop to process his photos.

When I saw his photos and compared them to mine the first thing that I saw,
was that color saturation in all of his photos looks to me rather small. Some
photos actually look a little pastel-colored and there is some yellow tint in
quite all of his photos. Color is not completely wrong but looks in my eyes  a
little strange.

I looked at the photos XMP metadata where I found a Photoshop section. In this
section there is an entry "ICCProfile" with a value of "Adobe RGB (1998)".

- Does this mean that color in these JPGs is in Adobe RGB 1998 and not in
sRGB? If yes then perhaps this difference in colorspace could be the reason
for the pale colors, couldn't it?

- What should digikam actually do with a photo that is in Adobe RGB color
space?  Would it be automatically convert it to sRGB when I look at it? Do I
have to activate colormanagement in digikam to get things right even if I just
want to look at these photos?

- Can a JPG actually contain an image in Adobe RGB or is (or should be) the
colorspace by definition sRGB in all JPGs?

I am actually unsure if I really have a color problem or if everything is the
way it should be, but since my friend does not live next door I cannot just
take a look on his monitor to see if he intended this "special" color look.

Thanks for your help
Rainer

--
Rainer Krienke, Uni Koblenz, Rechenzentrum, A22, Universitaetsstrasse  1
56070 Koblenz, http://www.uni-koblenz.de/~krienke, Tel: [phone]
PGP: http://www.uni-koblenz.de/~krienke/mypgp.html,Fax: [phone]

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[krienke]

Am Samstag, 13. Juni 2009 schrieb Gys van Zyl:
> I don't use the color management features of digiKam, so I can't give you
> any guidance there.  What you can do is to open one of his jpegs in Gimp
> and choose to convert to sRGB when Gimp prompts to do so.  You will then
> have a better idea of what your friend intended the photo to look like.
>

Hy Gys,

I tried gimp. Showing image properties in gimp it tells me that the color
profile is Adobe RGB 1998. If I activate Colormanagement and say that gimp
should use the system profile for my screen, then  colors are shown different.
Saturation is higher and there is more red in the photo. So this looks better.

So I guess I have to activate colormanagement in digikam as well. I set
display and working profile to sRGB. But if I open an photo in imageeditor
which I also use to take a detailed look at photos, it wants to convert the
photos colorspace (just by loading it), but I just want to look at it but not
change it, just the way it works in gimp. Any idea how?

Thanks
Rainer

--
Rainer Krienke, Uni Koblenz, Rechenzentrum, A22, Universitaetsstrasse  1
56070 Koblenz, http://www.uni-koblenz.de/~krienke, Tel: [phone]
PGP: http://www.uni-koblenz.de/~krienke/mypgp.html,Fax: [phone]

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[Paul Waldo]

Hi Rainer,

Have you calibrated your monitor?  This is the process of adjusting your monitor's controls so that your color display is standard.  It makes sure that you get the highest dynamic range possible and that there are no color casts.

KDE has a rudimentary calibration tools in Display|Gamma.  I'm not wild about it, but it may work for you.  I use gammaPage, available at http://www.pcbypaul.com/software/GAMMApage.html.  It works similarly to Abobe Gamma, but also allows you to see if you have an overall color cast.  Hope that helps!

Paul
----- "Rainer Krienke" <[hidden email]> wrote:

> Hello,
>
> i run digikam 0.10 on my openSuSE 11.1 box. All my photos are in sRGB
>
> colorspace. JPG files I convert from my cameras NEF files (using
> bibble) are
> also in sRGB. In digikam colormanagement is disabled. So far so good.
> Up to
> now I never had any color problems.
>
> Today a friend send me some JPG photos. I know he also shoots in RAW
> (Nikon
> D300) and then converts these files into either tiff or JPG. We spent
> a
> holiday together and now exchanged some photos, he sent me JPG files.
> He is
> working with windows, I guess to remember he is using Nikon Capture
> and Adobe
> Photoshop to process his photos.
>
> When I saw his photos and compared them to mine the first thing that I
> saw,
> was that color saturation in all of his photos looks to me rather
> small. Some
> photos actually look a little pastel-colored and there is some yellow
> tint in
> quite all of his photos. Color is not completely wrong but looks in my
> eyes  a
> little strange.
>
> I looked at the photos XMP metadata where I found a Photoshop section.
> In this
> section there is an entry "ICCProfile" with a value of "Adobe RGB
> (1998)".
>
> - Does this mean that color in these JPGs is in Adobe RGB 1998 and not
> in
> sRGB? If yes then perhaps this difference in colorspace could be the
> reason
> for the pale colors, couldn't it?
>
> - What should digikam actually do with a photo that is in Adobe RGB
> color
> space?  Would it be automatically convert it to sRGB when I look at
> it? Do I
> have to activate colormanagement in digikam to get things right even
> if I just
> want to look at these photos?
>
> - Can a JPG actually contain an image in Adobe RGB or is (or should
> be) the
> colorspace by definition sRGB in all JPGs?
>
> I am actually unsure if I really have a color problem or if everything
> is the
> way it should be, but since my friend does not live next door I cannot
> just
> take a look on his monitor to see if he intended this "special" color
> look.
>
> Thanks for your help
> Rainer
>
> --
> Rainer Krienke, Uni Koblenz, Rechenzentrum, A22, Universitaetsstrasse
> 1
> 56070 Koblenz, http://www.uni-koblenz.de/~krienke, Tel: [phone]
> 1312
> PGP: http://www.uni-koblenz.de/~krienke/mypgp.html,Fax: [phone]
> 1001312
>
> _______________________________________________
> Digikam-users mailing list
> [hidden email]
> https://mail.kde.org/mailman/listinfo/digikam-users

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[Milan Knížek]

Rainer Krienke píše v So 13. 06. 2009 v 13:35 +0200:
> Hello,
>
> i run digikam 0.10 on my openSuSE 11.1 box. All my photos are in sRGB
> colorspace. JPG files I convert from my cameras NEF files (using bibble) are
> also in sRGB. In digikam colormanagement is disabled. So far so good. Up to
> now I never had any color problems.
>
Assuming your display device has a similar colour characteristics as
sRGB, this is really the easiest way to go.


> I looked at the photos XMP metadata where I found a Photoshop section. In this
> section there is an entry "ICCProfile" with a value of "Adobe RGB (1998)".
>
> - Does this mean that color in these JPGs is in Adobe RGB 1998 and not in
> sRGB? If yes then perhaps this difference in colorspace could be the reason
> for the pale colors, couldn't it?
>
Yes.
> - What should digikam actually do with a photo that is in Adobe RGB color
> space?  Would it be automatically convert it to sRGB when I look at it? Do I
> have to activate colormanagement in digikam to get things right even if I just
> want to look at these photos?
That's a question. There is a setting to automatically convert to the
working colour space or to ask the user. I would prefer to have another
option - to preserve the image's colour space as is without asking.
>
> - Can a JPG actually contain an image in Adobe RGB or is (or should be) the
> colorspace by definition sRGB in all JPGs?
>
JPEG can contain data in various target colour spaces - that depends on
user. To let the application know, what is the colour space, the icc
profile can be either embedded in jpeg (which make the file bigger), or
various tags can used for the standard profiles (exif.colorspace,
jpeg.colorspace). This information can be even conflicting and the
standard sets precedence of the data (which should be used in preference
before others).

You can use exiv2 or identify from ImageMagick to find out the details
(command line programs).

$ identify -verbose image.jpg
or
$ exiv2 -pa image.jpg

> I am actually unsure if I really have a color problem or if everything is the
> way it should be, but since my friend does not live next door I cannot just
> take a look on his monitor to see if he intended this "special" color look.
>
Well, I have just started with digiKam recently so I am not fully sure how the colour
management implementation is supposed to work there.

So far, when comparing image displayed by colour managed CinePaint or
GIMP and digiKam (Image View, Image Editor) looks different. It might
be worth going through the documentation and reported bugs to find out more.

br,

Milan Knizek
knizek (dot) confy (at) volny (dot) cz
http://www.milan-knizek.net - About linux and photography (Czech
language only)

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[krienke]

Am Samstag, 13. Juni 2009 13:35:13 schrieb Rainer Krienke:
> Hello,
>
> i run digikam 0.10 on my openSuSE 11.1 box. All my photos are in sRGB
> colorspace. JPG files I convert from my cameras NEF files (using bibble)
> are also in sRGB. In digikam colormanagement is disabled. So far so good.
> Up to now I never had any color problems.
>
> Today a friend send me some JPG photos. I know he also shoots in RAW (Nikon
> D300) and then converts these files into either tiff or JPG. We spent a

Hello,

thanks for you answers. In between I solved the problem. The source of trouble
was really the ADOBE RGB colorspace that had been used for the photos of my
friend.  I converted all of them to sRGB. The only thing I had to else then
was to reduce saturation since all photos were clearly oversaturated after
conversion to sRGB.  

Since i did not see a batch feature for this in digikam (I had about 300
photos) I used bibble for this after all, where this could be done with a
select all photos keyboard shortcut 1 more mouse click to adjust saturation
and another key press to start conversion.  Now digikam displays the jpgs
correctly and I can stay with color management turned off.

I think for digikam it would be helpful to have a way to look at a photo in
another color space where digikam should convert colors on the fly (without
changing the photo and trying to write it to disk and a batch conversion that
can do this for all photos at once.  

Thanks
Rainer
--
Rainer Krienke, Uni Koblenz, Rechenzentrum, A22, Universitaetsstrasse  1
56070 Koblenz, http://www.uni-koblenz.de/~krienke, Tel: [phone]
PGP: http://www.uni-koblenz.de/~krienke/mypgp.html,Fax: [phone]


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[Gilles Caulier-4]

2009/6/15 Rainer Krienke <[hidden email]>:

> Am Samstag, 13. Juni 2009 13:35:13 schrieb Rainer Krienke:
>> Hello,
>>
>> i run digikam 0.10 on my openSuSE 11.1 box. All my photos are in sRGB
>> colorspace. JPG files I convert from my cameras NEF files (using bibble)
>> are also in sRGB. In digikam colormanagement is disabled. So far so good.
>> Up to now I never had any color problems.
>>
>> Today a friend send me some JPG photos. I know he also shoots in RAW (Nikon
>> D300) and then converts these files into either tiff or JPG. We spent a
>
> Hello,
>
> thanks for you answers. In between I solved the problem. The source of trouble
> was really the ADOBE RGB colorspace that had been used for the photos of my
> friend.  I converted all of them to sRGB. The only thing I had to else then
> was to reduce saturation since all photos were clearly oversaturated after
> conversion to sRGB.
>
> Since i did not see a batch feature for this in digikam (I had about 300
> photos) I used bibble for this after all, where this could be done with a
> select all photos keyboard shortcut 1 more mouse click to adjust saturation
> and another key press to start conversion.  Now digikam displays the jpgs
> correctly and I can stay with color management turned off.
>
> I think for digikam it would be helpful to have a way to look at a photo in
> another color space where digikam should convert colors on the fly (without
> changing the photo and trying to write it to disk and a batch conversion that
> can do this for all photos at once.

In digiKam 1.0.0, a Batch Queue Manager is implemented with some base tools.

Fill a wish to bugzilla if you want to see a "Color Space converter"
in the future. And don't forget to explain exactly what the tool must
do... because we switch between bugs step by step and we become crazy
with all different situations to handle.

Please no need to be verboze. Go to essential. No need to write a book
(i remember a guy who has written around 200 lines in B.K.O to explain
what he want... the wish is purely dropped to the trash (:=)))

Best

Gilles Caulier

>
> Thanks
> Rainer
> --
> Rainer Krienke, Uni Koblenz, Rechenzentrum, A22, Universitaetsstrasse  1
> 56070 Koblenz, http://www.uni-koblenz.de/~krienke, Tel: [phone]
> PGP: http://www.uni-koblenz.de/~krienke/mypgp.html,Fax: [phone]
>
>
> _______________________________________________
> Digikam-users mailing list
> [hidden email]
> https://mail.kde.org/mailman/listinfo/digikam-users
>
>

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Hi
I've submitted the wish "Color Space converter" to bugzilla
https://bugs.kde.org/show_bug.cgi?id=196730

p.s. thank you for great work!!!

> Fill a wish to bugzilla if you want to see a "Color Space converter"
> in the future. And don't forget to explain exactly what the tool must
> do... because we switch between bugs step by step and we become crazy
> with all different situations to handle.
>
> Please no need to be verboze. Go to essential. No need to write a book
> (i remember a guy who has written around 200 lines in B.K.O to explain
> what he want... the wish is purely dropped to the trash (:=)))
>
> Best
>
> Gilles Caulier
>

--
Wbr,
Nikita


"Linux doesn't dictate how I work, I dictate how Linux works."
(c) Eric Crampton
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