About wide vs. small gamuts, 8 vs. 16-bit &sRGB vs. Adobe'98

Started Apr 3, 2003 | Discussions thread
OP Magne Nilsen Senior Member • Posts: 1,120
Re: Very nice. But what does...

alFR wrote:

I understood that from version 7, if you opened a document with a
colour profile embedded Photoshop used that colourspace as the
working space e.g. open a sRGB-tagged image, you edit in sRGB. I
thought that the working space set within PS only determined the
colourspace for new documents or those without an assigned profile.
Is that correct?

Generally it will "Use the embedded profile" if you say so, but this all depends on, and is controlled by your settings inside PhotoShops Edit-Color Settings:

and your selected Working Space in the same dialog.

As an aside, there was a big debate over at Robgalbraith.com about
whether to convert documents to your working space or not, i.e. if
you open a D60 image that has the sRGB (or a custom) profile
assigned, should you convert it to AdobeRGB for editing or just
leave it. Ian Lyons was of the opinion that you should just leave
it, as the conversion to AdobeRGB wouldn't yield any real-world
benefits and might degrade the image slightly. His argument seemed
logical and now I've stopped converting to AdobeRGB as part of my
workflow. Comments anyone?

I am very much on Ian's side in this. Any color space conversions has an element of rounding errors and quantization problems in them, and as long the original color space is a real working space with the same gamma values (2.2) - like sRGB or AdobeRGB - and not a device profile space (like a camera/scanner gamut) I would advice to stay in the original color space.

A typical "convert to profile" conversion means going "down" to a gamma 1.0 wide Lab space - and then back to a gammacorrected less-wide space again. Adobe has stated that those conversion are always done in 16-bit no matter if the image is 8-bit, but a typical down to gamma 1.0 and back to gamma 2.2 is still a big conversion...

The critical aspect is often to know when "real-world benefits" occurs and when "real-world problems" occurs. Many of the AdobeRGB (and even wider gamuts) proponents often wants a simple answer for a complex question. Unfortunately, real life (or politics) often doesn't behave like that.

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Magne

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