Re: about negs and ROMM / Pro Photo RGB
Re: about negs and ROMM / Pro Photo RGB
- Subject: Re: about negs and ROMM / Pro Photo RGB
- From: email@hidden (Bruce Fraser)
- Date: Thu, 2 Aug 2001 17:56:31 -0700
At 8:02 PM +0000 8/2/01, neilB wrote:
fellow geeks
Some have expressed the opinion that since, when working with
neg. scans, the gamut can be massive when converted - perhaps it's
worth working in ProPhoto [nee ROMM] until the 16 bit work is
done.
Remembering, of course, I imagine, [to archive 16 bit first then]
to convert to A-RGB or similar before leaving 16 bit world.
It'd probably worth being choosy about intents on the way in to
and from ProPhoto - but it seems that all inter-workingspace
conversions are probably Perceptual since most workingspaces
[including ProPhoto seem to lack any Colorimetric tags.
Now - a while back someone [Bruce?] did some testing with ROMM
and I think he wrote something about keeping away from the
endpoints of the histogram - like no data above 140 or so and
none below 10, was that because he feared gamut compression on
conversion to - say A-RGB - or for a less obvious reason??
Am I remembering this right?
thanks for the input
neilB
Neil Barstow
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It's quite true that color negs can hold a massive color gamut and
dynamic range, but that's not exactly why I use ProPhoto for neg
scans.
What I do with color neg is to scan them as raw 16-bit images,
letting the scanner software (Imacon ColorFlex) convert the raw scan
from Imacon RGB to ProPhoto. The result is invariably flat,
unsaturated, and color-casted, but it's very easy to correct. I start
by removing the color cast, then I shape the tone, and as I do so,
the saturation increases too (since when you add contrast, you're
forcing more pixels towards 0 and 255.
I stay away from extreme values in a single channel because in
ProPhoto the primaries are not real colors, and if you produce a
saturated color in ProPhoto the results can be quite strange.
I don't usually convert to another working space before going to output.
Conversions between working spaces, and conversions into working
spaces from capture spaces, are ALWAYS relative colorimetric. The
tables may say they're preceptual, but I bet you dollars to doughnuts
you'll get identical results using RelCol and Perceptual...
Bruce
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