[Digikam-users] ICC file for Ricoh GXR

[Remco Viëtor]

On Friday 20 July 2012 19:58:48 Martin wrote:
> > That is not the case, a camera profile is used to modify the colours
> > saved in the RAW file when they are turned into what is displayed on 
the
> > computer or stored in a colour-corrected TIFF, JPEG etc. 
> 
> Not quite right. The camera profile is used to transfer the data from
> raw processor (after demosaicing ...) into the working colour space
> (that are usually sRGB, prophotoRGB, eciRGB) which are transfered into
> the display (or storage or print) colour space (sRGB, AdobeRGB ...). The
> extra step with the working colour space is used to get a defined base
> for further transformation.

Just to dot all the i's and cross all the t's:
That's not quite rigth (or quite complete) either.

Let's first define what we are talking about:
- for me, the camera *profile* is a correction curve to compensate the 
differences between what a colour should be and what it is in practice 
(strictly the same as what a display or printer profile does);
- in addition, there's a camera *working space*, which defines how the 
camera encodes the colours it sees. 
The working space is essential, unchangeable, and present in the RAW 
decoders (implicit or explicit).

So, a camera profile is not strictly required (then we assume that the 
camera has no deviations in the colour representation),which is where the 
advice "don't worry about it unless you have special needs" came from.

So now we have our colours in our photo editor, in a well defined colour 
space. If your editing working space corresponds to the device's working 
space, no further transfer is necessary (device profiles still have to be 
applied though).

And the 'extra step' with the working colour space is not extra at all, it 
is a essential step in the process, as that is the first step where your 
colours are well defined across devices/systems. 

And for quite a few uses, there's no need to translate from one colour 
space to another. For screen display the (de facto) standard is sRGB (with 
some high-end displays having the ability to use Adobe RGB), and most print 
shops also accept only sRGB. (some printers can handle Adobe RGB).

And indeed, colour management involved a lot of steps, and is complex...

Remco

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