large gamut color space

I was just reading a post from Colin about color space (related to Firefox).
there, he mentioned that given the 8 bits encoding for each primary color, we got a max number of combination of 16 millions or so...

now, given that encoding is the same on any color space, if you have a large gamut color space (say ProPhoto), maybe you get more possible colors , but you are also spreading those values to reach those corners of the gamut...

so if you have a pic that has lots of variations around the same color, I would think that all color variants would not be encoded in a large Gamut color space, but could actually gain using a smaller gamut, bc there will be more possible encoded values into that small color variation spectrum...

did I miss anything?
Vincent

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Originally Posted by atvinnys

did I miss anything?

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Yes and no :)

I don't recall saying anything about 3x 256 bit channels adding up to the 16M colours etc (even though they do), although I did post about using 8 bit (256 colours per channel) as it applies to absolute levels in gamuts (re displaying in non-colour-managed browsers), which is probably what you're referring to.

Quote:

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Originally Posted by atvinnys

now, given that encoding is the same on any color space, if you have a large gamut color space (say ProPhoto), maybe you get more possible colors , but you are also spreading those values to reach those corners of the gamut..."

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Yes. Keep in mind also that "conceptually" the gamut of the human eyes is also very limited compared to what some colour spaces are capable of representing (in a kind of backward looking kind of way!).

Quote:

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Originally Posted by atvinnys

so if you have a pic that has lots of variations around the same color, I would think that all color variants would not be encoded in a large Gamut color space, but could actually gain using a smaller gamut, bc there will be more possible encoded values into that small color variation spectrum..."

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Excellent observation - and this is the reason one should never, ever, use 8 bit colour (256 bits per channel) on large spaces - you need to use 16 bit (of which photoshop actually uses 15 bits per channel) which gives you 32,756 possible steps per channel (up slightly from 256!) - I was only using the 8 bit representation to make the concept of why a large-gamut encoded image looks dull & unsaturated if the displaying application incorrectly assumes that it's sRGB.

There's a raging debate going on over 8-Bit -v- 16-bit manipulation, with little agreement - what little agreement that many do have however is that the potential does exist for image degradation for large changes in big spaces with 8 bit representation. Personally, I just do everything in 16 bit - it errs on the safe side, and I don't have size or performance issues on my processing PC. Printing often needs to be 8 bit for many, but since I do all of my own, this doesn't affect me either (I often just leave the images in LAB colour - my favourite working space).

Cheers,

Colin - pbase.com/cjsouthern

colin,

thanks for the answer...for some reason I got stuck with 8 bits....

You're welcome,

The whole 8/16 bit thing and the many different colour spaces is something that trips up a lot of people - I've been guilty of having a quick print done in town (one not worth cranking my printer up for) - only to discover I've left it in ProPhoto and have to fix it and print it again, but unfortunately that's the way it works for now.

Cheers,

Colin - pbase.com/cjsouthern