On Jun 1, 2005, at 6:22 AM, Jón A Sandholt wrote:

This is a very interesting discussion, wich I have been following with great interest.

I have a question that relates to this topic.

How does bit depth ( 8 bit vs 16 bit etc.) relate to all this.We are told that 8 bit color can give us about 16,7 million colors and 16 bit something much more (I don't wont even try to do the calculations).I know this is only in theory but lets say you have a 8 bit image in ProPhoto RGB and one thats 16 bit in the same colorspace, is there a difference between them as to how much part of the space they use?
What I'm trying to say is does a high bit image make a better use of a large colorspace than the 8 bit one?
Am I missing some point here or misunderstanding something?

Bruce has said a number of times on various lists and to me as well that Prophoto RGB 8-bit/channel images can take more abuse than one might suspect. I don't have an anecdote or rule of thumb really, to indicate when there would be a problem. There are two schools of thought: a.) work in 8-bits/channel until you have a problem that's related to bit-depth then start over in 16-bits/channel; b.) work in 16-bits/channel even though a fair majority of the time there may be no point in doing so.

It really depends on what kind of work you do, what kind of edits you do, what's in the image (gradients of course are more susceptible to posterization than noisy areas), etc.

Chris Murphy

Color Remedies (TM)

www.colorremedies.com/realworldcolor

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Co-author "Real World Color Management, 2nd Edition"

Published by PeachPit Press (ISBN 0-321-26722-2)