[Digikam-users] Re: SRBG, Adobe RGB, What to use ?

[Martin (KDE)]

Am Sonntag, 26. Juni 2011 schrieb Remco Viëtor:
> on Sunday 26 June 2011, Patrick Op de Beeck wrote:
> > On the my Lumix is the choice between Adobe RGB and sRGB.
> > 
> > What are the advantages/disadvantages of both settings ?
> > What should I use with Digicam ?
> > Does it have any effect on RAW pictures ?
> > 
> > Patrick
> > _______________________________________________
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> 
> To start with the last question: No, your choice of colour space
> doesn't have an effect on your RAW files.
> And, You can use both with Digikam.  (that was easy ;) )
> 
> Now for the harder bit:
> 
> The main difference between the 2 colour spaces is that Adobe RGB
> has a larger gamut (can express more colours) than sRGB. BUT: most
> screens and printers can only use/display sRGB, so an image using
> Adobe RGB will not display/print correctly in such a case. At best
> you will get a transformation to sRGB 'on the fly', at worst your
> images will look very flat and dull.

Just some small additions: The advantage of AdobeRGB only depends on 
the output system supporting colour management or not. This is very 
unlikely for most "normal" users and many printing labs. There are 
some out there doing a consequent colour management. And there are 
some users using wide gamut displays and colour management. They can 
use AdobeRGB and they can see the benefits of if (if available). Not 
every picture needs a wider gamut.

A big disadvantage of AdobeRGB (and other colour spaces) with jpeg 
files is the limited range of available bits. For standard jpeg you 
have 8 bits per colour channel (RGB). The wider your gamut the bigger 
the steps between two values.

If you use a colour space with double range of blue compared to sRGB 
(as an example) you still have only 256 different types of blue. If 
your photo uses the complete range your are fine. If your photo uses 
only the range defined in sRGB you have only 128 different steps of 
blue So you loose quality. (This assumes the colour spaces are linear 
which they are not but it is easier to compare).

AdobeRGB is only a little bit bigger than sRGB so the advantage is 
only limited. If you need bigger colour spaces shoot raw photos and 
use a really big colour space (ProPhoto or similar) with at least 16 
bit.

> 
> If, like most people, you have your photos printed commercially,
> your best (only?) bet is to stick to sRGB.
> 
> Only if you print your images yourself and you have a printer
> capable of printing Adobe RGB, you could study the differences and
> decide what to use.

Or you can be sure the photo lab uses colour management.

Martin

> 
> The above is just a very quick answer, you'll need to search for
> more in-depth texts to really understand what's going on.
> 
> Remco
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