[Digikam-users] Printers with full Color Management

[Gilles Caulier]

2009/10/4 Milan Knížek <knizek.confy at volny.cz>:
> Gerhard Kulzer píše v Ne 27. 09. 2009 v 08:55 +0200:
>> On Friday 04 September 2009 09:47:24 pm Milan Knížek wrote:
>> >
>> > AFAIK, the thing is that not all converters apply the same steps in the
>> > same order and that some of the steps are variables affecting the raw
>> > and rgb data. Some of the settings can be set by the user, some may be
>> > hidden (and proprietary).
>> >
>> > E.g. UFRaw applies white balance, highlight-reconstruction, wavelet
>> > de-noising, raw curve adjustment, gamma and linearity before
>> assignment
>> > of the camera profile.
>> >
>> > Next problem is that the camera sensor does not react fully linearly to
>> > the light - hence an icc profile prepared for a particular
>> > white-balance/raw curve/etc. and used for another
>> > white-balance/curve/etc may provide different result even in the same
>> > raw converter.
>> >
>> > If my understanding is wrong, I would be more then happy to know other
>> > opinions.
>> >
>> > P.S.2 The difference is quite obvious when using Canon's Digital Photo
>> > Professional and UFRaw. There are methods how to find out, which ICC
>> > profiles are used by DPP in MS Windows. However, people were usually
>> not
>> > able to get the same output from UFRaw with those profiles. (I tried
>> > myself and skipped this approach - the Adobe Matrices in dcraw based
>> > converters provide better results).
>> At least theoretically you are wrong in the sense that color management
>> should be independent of MS or Linux or whatever, it's the very sense of it.
>> CM transforms an image from one color space into another by transiting
>> through an ideal color space, it's a mathematical operation not dependent
>> on any drivers.
>> But then there is the question as to whether the CM has been correctly
>> implemented by a specific program or driver.
>
> That is misunderstanding of the previous discussion - while we can
> assume the differences between CM engines are reasonably small, the
> first problem of impossibility to use DPP's ICC profiles for UFRaw lays
> with the fact that different image data are fed to the CM engine. I.e. I
> also agree with your statement (on the theoretical level).
>
> In another words, if UFRaw was able to "develop" the same image data as
> DPP does (i.e. demosaic, denoise, curve, white-balance, whatever
> else...), then we could use DPP's ICC profiles in UFRaw, too.

This is a strong manner to understand CM...

An ICC profile is an undependable OS/software color lut data used in a
standard war to adjust color/gamma/conversion from a color space to
another one.

In this data camera/printer/screen maker set a lots of standardized
information relevant of device. The way to use these information is
described in a CM paper from ICC working group.

Adobe, M$, and some open source project implement these standardization.

In other way, an ICC profile do not depand of an OS/Software !
Personally, i use ICC caera color profile provided from Minolta Win32
program under Linux without any problem.

But, where you has right, some makers as Nikon and Canon, provide ICC
profile with uncomplete or with not standardized data ! ICC profiles
become proprietary and only work with makers software.

This is really weird !

Gilles Caulier