Conversion to any other color model and back again will always cost
something; doing it repeatedly will cause increasing losses. Working
in any one color model exclusively minimizes losses (I stick with RGB).
I do all such editing using Adjustment Layers. You can set them to
adjust Luminance only, which minimizes color shifting regardless of
whether you are working in 8bit or 16bit RGB, and does not touch the
base data. Once you've achieved the rendering you want and saved the
layered file, you can perform the rendering and do all the
calculations just once by flattening layers, then saving to a new file.
Godfrey
On Oct 13, 2005, at 3:44 AM, Frantisek wrote:
With some photographs in need of heavy brightness editing (e.g. heavy
burning/dodging and curves, e.g. underexposed photos), what is the
best colour model to edit in? Editing in plain RGB often makes huge
hue shifts, which make it ugly especially if the edit is local only.
Editing in L from LAB mode leaves all colours severely desaturated
upon "exposure" boost (but keeps the hue, unlike RGB), requiring a
Saturation boost afterwards (but it's hard to tell how much will be
needed, to bring it back to normal). I guess it's because of nonlinear
gamma that the RGB photos make hue changes upon changing brightness.
How about reversing the gamma curve to linear (when one knows the
exact curve), brightening and applying gamma again?
What I also tried is editing in HSB and HSL spaces. These preserve hue
and saturation upon editing of B/L (unlike LAB space), with the best
so far seemingly the HSB space, where the channels do not clip as with
RGB heavy levels/curves change, nor are there any colour shifts as
with RGB. I can recommend it, but I don't know if it's suitable for
all photographs - I know very little about these colour modes, what
do others thing
about editing in them? Could there be some problems? And if it is so
much better to change tonality in HSB, why the heck Adobe hasn't yet
implemented it directly?
Thanks for comments,suggestions,et cetera. Are there some Curves/...
plugins that make editing in other than RGB easier? Now it's a bit
tedious - the Adobe plugin "HSB/HSL" is quite awkward to use.
Frantisek
