Color Management Jeopardy

[Elle Stone]

Several years ago, I put together a Color Management Tutorial for the digiKam documentation. I wrote it as a series of "Questions and Answers" based on questions that were asked from time to time in the digiKam users forum.

A couple of months ago I looked at the html version of that Tutorial (http://docs.kde.org/development/en/extragear-graphics/digikam/raw-decoding.html) and discovered to my dismay that most of the Questions weren't included with the Answers, making it not so much a Tutorial as a game of Color Management Jeopardy (here's the answer: "Glad you asked. All digital camera images start out as raw files . . . " - now try to guess the question).

So I've written an entirely new tutorial and posted it to my website:

http://ninedegreesbelow.com/2011/imaging/color-management-tutorial/color-management-tutorial-table-of-contents.html

The rewrite is a whole lot better than the original, at least in my humble opinion. If anyone cares to look it over, feedback is welcome.

Here's a link to the page which answers the burning question, "Which digiKam buttons do I push"?

http://ninedegreesbelow.com/2011/imaging/color-management-tutorial/color-management-settings-behavior-tab.html

The Tutorial isn't quite finished. If there is a topic you are especially interested in that I haven't covered, or if I've made mistakes, I'll be grateful for your input.

Elle Stone

[Graham Dicker]

On Sunday 13 Mar 2011 23:04:02 Elle Stone wrote:

> Several years ago, I put together a Color Management Tutorial for the
> digiKam documentation. I wrote it as a series of "Questions and Answers"
> based on questions that were asked from time to time in the digiKam users
> forum.
>
> A couple of months ago I looked at the html version of that Tutorial
> (http://docs.kde.org/development/en/extragear-graphics/digikam/raw-decoding
> .html) and discovered to my dismay that most of the Questions weren't
> included with the Answers, making it not so much a Tutorial as a game of
> Color Management Jeopardy (here's the answer: "Glad you asked. All digital
> camera images start out as raw files . . . " - now try to guess the
> question).
>
> So I've written an entirely new tutorial and posted it to my website:
>
> http://ninedegreesbelow.com/2011/imaging/color-management-tutorial/color-ma
> nagement-tutorial-table-of-contents.html
>

<snipped>

Great article I will need to read it a couple more times before I can really
get my head around it. First question that I have is how do I deal with the
raw images out of my Pentax K200D? There is no embedded profile in the raw
files and I cannot find one for this camera anywhere on the internet. On the
CD that came with the camera there are icc files for sRGB and AdobeRGB but I
don't know if these have any bearing on the processing of PEF/DNG files.

Graham Dicker
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[Martin (KDE)]

Am 15.03.2011 16:38, schrieb Graham Dicker:

> On Sunday 13 Mar 2011 23:04:02 Elle Stone wrote:
>> Several years ago, I put together a Color Management Tutorial for the
>> digiKam documentation. I wrote it as a series of "Questions and Answers"
>> based on questions that were asked from time to time in the digiKam users
>> forum.
>>
>> A couple of months ago I looked at the html version of that Tutorial
>> (http://docs.kde.org/development/en/extragear-graphics/digikam/raw-decoding
>> .html) and discovered to my dismay that most of the Questions weren't
>> included with the Answers, making it not so much a Tutorial as a game of
>> Color Management Jeopardy (here's the answer: "Glad you asked. All digital
>> camera images start out as raw files . . . " - now try to guess the
>> question).
>>
>> So I've written an entirely new tutorial and posted it to my website:
>>
>> http://ninedegreesbelow.com/2011/imaging/color-management-tutorial/color-ma
>> nagement-tutorial-table-of-contents.html
>>
> <snipped>
>
> Great article I will need to read it a couple more times before I can really
> get my head around it. First question that I have is how do I deal with the
> raw images out of my Pentax K200D? There is no embedded profile in the raw
> files and I cannot find one for this camera anywhere on the internet. On the
> CD that came with the camera there are icc files for sRGB and AdobeRGB but I
> don't know if these have any bearing on the processing of PEF/DNG files.

Hallo Graham

Most likely the manufactures colour profiles are useless for handling
with digikam (or any other free raw development tool). So either trust
the default colour profiles of digikam or create one by your own.

As I already said: colour profiles are a little overestimated. You only
need this, if you have to relay on colour correctness (product photos
and similar). With this you need a complete colour calibrated setup
(this includes your monitors, printers and your light in your working
rooms).

So, first work with all available settings (try ufraw or darktable if
raw development of digikam is not sophisticated enough). And if you
still have problems with colours try profiling your camera.

>
> Graham Dicker

Martin
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[Elle Stone]

On 3/15/11, Graham Dicker <[hidden email]> wrote:
> First question that I have is how do I deal with the
> raw images out of my Pentax K200D? There is no embedded profile in the raw
> files and I cannot find one for this camera anywhere on the internet. On the
> CD that came with the camera there are icc files for sRGB and AdobeRGB but I
> don't know if these have any bearing on the processing of PEF/DNG files.
>

Hi Graham,

I haven't finished exploring the digiKam raw converter. But there are
three choices for the camera profile: "None", "Embedded", and
"Custom".

"None":
I assume that "None" means use the default camera matrix in the dcraw
code. That's the only logical conclusion, and the output using "None"
is identical with UFRaw output, after adjusting for exposure. The only
thing is, if you use any "Workspace" color space other than sRGB,
digiKam doesn't seem to handle the Tone Response Curve ("gamma")
correctly. (TRCs aren't always a true gamma curve; sRGB doesn't have a
true gamma TRC; digiKam seems hard-coded to use the default dcraw TRC,
which may or may not be exactly the same as sRGB - I'm too lazy to
track down the answer - but the default dcraw TRC is most definitely
not a true gamma curve.)

The digiKam raw converter uses libraw, which gets its camera matrices
from the dcraw c-code. dcraw c-code does have a camera matrix for the
K200D:

 { "PENTAX K200D", 0, 0,
        { 9186,-2678,-907,-8693,16517,2260,-1129,1094,8524 } }

The matrix above is what is used to convert your interpolated raw file
from the "raw" color to a working space.

"Embedded":
"Embedded" is an option from the dcraw code that only applies to a few
cameras. Quoting from the dcraw documentation
(http://www.cybercom.net/~dcoffin/dcraw/dcraw.1.html):

"+M or -M Use (or don't use) any color matrix from the camera
metadata. The default is +M if -w is set, -M otherwise. This option
only affects Olympus, Leaf, and Phase One cameras."


"Custom":
"Custom" requires that you have your own custom camera profile, for
which you'd need a target, the least expensive of which is made by
Wolf Faust (http://www.colorreference.de/targets/index.html - you'd
need to purchase the C1 target).

So I'm not sure how to respond to your question regarding the K200D -
is the problem that you aren't happy with the colors you are getting?
Or you are not sure about the digiKam settings to use? Or something
else altogether? (Feel free to send a private email if the problem
isn't really digiKam-related.)

Martin is correct when he says that the manufacturer's camera profile,
if you could even find one, isn't likely to work very well when using
any software other than the manufacturer's own proprietary raw
rendering software.

Many people (including myself) do choose to create their own custom
camera profile because they are not happy with the colors coming from
the default dcraw camera matrix. My own custom camera profiles are
simple, general purpose matrix profiles, just like the ones that dcraw
uses, only the colors are nicer. A lot of people who own Nikon and
Canon cameras feel that the default dng matrices produce anemic colors
for these cameras.

Elle
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[Gilles Caulier-4]

Elle,

In my TODO list, i must improve this CM panel in RAW Import tool to be
able to use digiKam CM settings from config dialog. The idea is to
provide the list of profile set and available in this settings to
simplifly configuration.

Gilles Caulier

2011/3/16 Elle Stone <[hidden email]>:

> On 3/15/11, Graham Dicker <[hidden email]> wrote:
>> First question that I have is how do I deal with the
>> raw images out of my Pentax K200D? There is no embedded profile in the raw
>> files and I cannot find one for this camera anywhere on the internet. On the
>> CD that came with the camera there are icc files for sRGB and AdobeRGB but I
>> don't know if these have any bearing on the processing of PEF/DNG files.
>>
>
> Hi Graham,
>
> I haven't finished exploring the digiKam raw converter. But there are
> three choices for the camera profile: "None", "Embedded", and
> "Custom".
>
> "None":
> I assume that "None" means use the default camera matrix in the dcraw
> code. That's the only logical conclusion, and the output using "None"
> is identical with UFRaw output, after adjusting for exposure. The only
> thing is, if you use any "Workspace" color space other than sRGB,
> digiKam doesn't seem to handle the Tone Response Curve ("gamma")
> correctly. (TRCs aren't always a true gamma curve; sRGB doesn't have a
> true gamma TRC; digiKam seems hard-coded to use the default dcraw TRC,
> which may or may not be exactly the same as sRGB - I'm too lazy to
> track down the answer - but the default dcraw TRC is most definitely
> not a true gamma curve.)
>
> The digiKam raw converter uses libraw, which gets its camera matrices
> from the dcraw c-code. dcraw c-code does have a camera matrix for the
> K200D:
>
>  { "PENTAX K200D", 0, 0,
>        { 9186,-2678,-907,-8693,16517,2260,-1129,1094,8524 } }
>
> The matrix above is what is used to convert your interpolated raw file
> from the "raw" color to a working space.
>
> "Embedded":
> "Embedded" is an option from the dcraw code that only applies to a few
> cameras. Quoting from the dcraw documentation
> (http://www.cybercom.net/~dcoffin/dcraw/dcraw.1.html):
>
> "+M or -M Use (or don't use) any color matrix from the camera
> metadata. The default is +M if -w is set, -M otherwise. This option
> only affects Olympus, Leaf, and Phase One cameras."
>
>
> "Custom":
> "Custom" requires that you have your own custom camera profile, for
> which you'd need a target, the least expensive of which is made by
> Wolf Faust (http://www.colorreference.de/targets/index.html - you'd
> need to purchase the C1 target).
>
> So I'm not sure how to respond to your question regarding the K200D -
> is the problem that you aren't happy with the colors you are getting?
> Or you are not sure about the digiKam settings to use? Or something
> else altogether? (Feel free to send a private email if the problem
> isn't really digiKam-related.)
>
> Martin is correct when he says that the manufacturer's camera profile,
> if you could even find one, isn't likely to work very well when using
> any software other than the manufacturer's own proprietary raw
> rendering software.
>
> Many people (including myself) do choose to create their own custom
> camera profile because they are not happy with the colors coming from
> the default dcraw camera matrix. My own custom camera profiles are
> simple, general purpose matrix profiles, just like the ones that dcraw
> uses, only the colors are nicer. A lot of people who own Nikon and
> Canon cameras feel that the default dng matrices produce anemic colors
> for these cameras.
>
> Elle
> _______________________________________________
> Digikam-users mailing list
> [hidden email]
> https://mail.kde.org/mailman/listinfo/digikam-users
>

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[david-vj]

CONTENTS DELETED

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[Marcel Wiesweg]

> With so many persons using so few (relatively) camera models I am really
> surprised that there is not a wealth of camera profile data sitting out
> there for common use.
>
> Canon, unfortunately, now bury their information in a welter of
> propitiatory files, it almost appears that this manufacturer is trying
> to force the world into its software. Shame!
>
> Maybe it needs the open-source community to assemble and disseminate
> reliable information.

The problem IMO is that there is no comprehensive CM solution for Linux. There
is ArgyllCMS, which is probably powerful, but cryptic.
In digikam, we attempt to do what we can within our scope, but there is no
system-wide profile register, no good support for setting a monitor profile
(I'm talking about a KDE-based UI), what about printing?
Let alone a wizard to guide throught the creation of a profile even if you
have bought a target and made a photo of it.

Marcel
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[Marcel Wiesweg]

> I haven't finished exploring the digiKam raw converter. But there are
> three choices for the camera profile: "None", "Embedded", and
> "Custom".

I agree there are rough edges with RAW file color management. One reason is
that the relevant widget is in libkdcraw, and color management is in digikam.
Second, specifying a single "input profile" falls short if you use more than
one camera.
Third, as you point out below, the options dont have a good usability.


> "None":
> I assume that "None" means use the default camera matrix in the dcraw
> code.

I agree

> That's the only logical conclusion, and the output using "None"
> is identical with UFRaw output, after adjusting for exposure. The only
> thing is, if you use any "Workspace" color space other than sRGB,
> digiKam doesn't seem to handle the Tone Response Curve ("gamma")
> correctly. (TRCs aren't always a true gamma curve; sRGB doesn't have a
> true gamma TRC; digiKam seems hard-coded to use the default dcraw TRC,
> which may or may not be exactly the same as sRGB - I'm too lazy to
> track down the answer - but the default dcraw TRC is most definitely
> not a true gamma curve.)

Suggestions at what point we need to improve are welcome ;-)

> Martin is correct when he says that the manufacturer's camera profile,
> if you could even find one, isn't likely to work very well when using
> any software other than the manufacturer's own proprietary raw
> rendering software.

Very important point IMO.

>
> Many people (including myself) do choose to create their own custom
> camera profile because they are not happy with the colors coming from
> the default dcraw camera matrix. My own custom camera profiles are
> simple, general purpose matrix profiles, just like the ones that dcraw
> uses, only the colors are nicer. A lot of people who own Nikon and
> Canon cameras feel that the default dng matrices produce anemic colors
> for these cameras.

What about sharing such profiles? We could easily setup a repository.



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[Martin (KDE)]

Am Mittwoch, 16. März 2011 schrieb David Vincent-Jones:
> With so many persons using so few (relatively) camera models I am
> really surprised that there is not a wealth of camera profile data
> sitting out there for common use.

There is no such thing like ONE camera profile. First: it is not the
camera you have to profile but the combination light-lens-camera. Next
you may need different kind of profiles (matrix, lut ...). Every user
has different requirements in the quality of the profile. There are
different calibration pattern out there (IT8, ...)

What do you need a profile for, if you know only one of this
parameter? I for myself build several profiles under different lights
and situations. It is not that easy to build a really good one. Just a
slightly bit of green in the background and your profile has to little
green. You need a reproducible environment. I only use self-made
profiles for special situations. For all others the default
(darktable) profiles are quite good.

For raw development I currently use darktable. This software uses some
general profiles (where available) and get really good results. But
the main point is not the profile, but the base curve. Only if the
colour (after white balance of course) is wrong there is a need of
profiling (or colour correction).

>
> Canon, unfortunately, now bury their information in a welter of
> propitiatory files, it almost appears that this manufacturer is
> trying to force the world into its software. Shame!

This is in no way different than Nikon (in some parts better in others
worse). I am not forced in any parts to use canon software for raw
developing. At least for linux there are lots of software out there
(digikam, ufraw, rawstudio, darktable, photivo - just to name the open
source ones). And some of them are realy good, even better than the
canon software. I think the same is true for Nikon.

>
> Maybe it needs the open-source community to assemble and
> disseminate reliable information.

As I already said, just a different lens with another coating and you
get a slightly blue shift (or may be yellow). Most likely this is not
visible but the same may be true for profiles as well.

Don't take me wrong: I like the idea of profiling and I use it. And
thanks to Graeme we have all tools we need to do it as open source.
And it may be worth the effort. But you have to take the effort by
yourself and profile your workflow.

Martin

>
> David
>
> On Wed, 2011-03-16 at 12:47 -0400, Elle Stone wrote:
> > On 3/15/11, Graham Dicker <[hidden email]> wrote:
> > > First question that I have is how do I deal with the
> > > raw images out of my Pentax K200D? There is no embedded profile
> > > in the raw files and I cannot find one for this camera
> > > anywhere on the internet. On the CD that came with the camera
> > > there are icc files for sRGB and AdobeRGB but I don't know if
> > > these have any bearing on the processing of PEF/DNG files.
> >
> > Hi Graham,
> >
> > I haven't finished exploring the digiKam raw converter. But there
> > are three choices for the camera profile: "None", "Embedded",
> > and "Custom".
> >
> > "None":
> > I assume that "None" means use the default camera matrix in the
> > dcraw code. That's the only logical conclusion, and the output
> > using "None" is identical with UFRaw output, after adjusting for
> > exposure. The only thing is, if you use any "Workspace" color
> > space other than sRGB, digiKam doesn't seem to handle the Tone
> > Response Curve ("gamma") correctly. (TRCs aren't always a true
> > gamma curve; sRGB doesn't have a true gamma TRC; digiKam seems
> > hard-coded to use the default dcraw TRC, which may or may not be
> > exactly the same as sRGB - I'm too lazy to track down the answer
> > - but the default dcraw TRC is most definitely not a true gamma
> > curve.)
> >
> > The digiKam raw converter uses libraw, which gets its camera
> > matrices from the dcraw c-code. dcraw c-code does have a camera
> > matrix for the
> >
> > K200D:
> >  { "PENTAX K200D", 0, 0,
> >  
> > { 9186,-2678,-907,-8693,16517,2260,-1129,1094,8524 } }
> >
> > The matrix above is what is used to convert your interpolated raw
> > file from the "raw" color to a working space.
> >
> > "Embedded":
> > "Embedded" is an option from the dcraw code that only applies to
> > a few cameras. Quoting from the dcraw documentation
> > (http://www.cybercom.net/~dcoffin/dcraw/dcraw.1.html):
> >
> > "+M or -M Use (or don't use) any color matrix from the camera
> > metadata. The default is +M if -w is set, -M otherwise. This
> > option only affects Olympus, Leaf, and Phase One cameras."
> >
> >
> > "Custom":
> > "Custom" requires that you have your own custom camera profile,
> > for which you'd need a target, the least expensive of which is
> > made by Wolf Faust
> > (http://www.colorreference.de/targets/index.html - you'd need to
> > purchase the C1 target).
> >
> > So I'm not sure how to respond to your question regarding the
> > K200D - is the problem that you aren't happy with the colors you
> > are getting? Or you are not sure about the digiKam settings to
> > use? Or something else altogether? (Feel free to send a private
> > email if the problem isn't really digiKam-related.)
> >
> > Martin is correct when he says that the manufacturer's camera
> > profile, if you could even find one, isn't likely to work very
> > well when using any software other than the manufacturer's own
> > proprietary raw rendering software.
> >
> > Many people (including myself) do choose to create their own
> > custom camera profile because they are not happy with the colors
> > coming from the default dcraw camera matrix. My own custom
> > camera profiles are simple, general purpose matrix profiles,
> > just like the ones that dcraw uses, only the colors are nicer. A
> > lot of people who own Nikon and Canon cameras feel that the
> > default dng matrices produce anemic colors for these cameras.
> >
> > Elle
> > _______________________________________________
> > Digikam-users mailing list
> > [hidden email]
> > https://mail.kde.org/mailman/listinfo/digikam-users
>
> _______________________________________________
> Digikam-users mailing list
> [hidden email]
> https://mail.kde.org/mailman/listinfo/digikam-users

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