Re: sRGB & Jazz
Re: sRGB & Jazz
- Subject: Re: sRGB & Jazz
- From: Jack Kelly Clark <email@hidden>
- Date: Thu, 22 May 2003 11:16:40 -0700
Roger Breton replied:
You don't say whether the scans are RGB to begin with but that is what I
assume. Now, it's very possible that the assumed 'internal' color space of
the scanner is 1.8 gamma based. That would account for the
incredible change of brightness you describe when you say you to
your image. As you know, does not use 1.8 but rather 2.2.
Yes, they are RGB scans. However, there was really no brightness
change, Roger, just an overall "improvement" in the color.The monitor
is calibrated monthly to D65, gamma 2.2 and the PS Color Settings are
properly set for our ICC workflow (Adobe RGB, plus we make custom
cmyk profiles for our print vendors using ProfileMaker and a
SpectrolinoSpectroscan). This has been working quite well for us
since late 1997 (Thanks Andrew). Our scans come from many sources,
but the majority has been Photo CD. Now that Photo CD is drying up
and blowing away, we're out "shopping."
As for bringing the overly saturated colors back to life, I would suspect
again that this is a function of your Photoshop default RGB Working Space
setup, most likely set to AdobeRGB? Especially if you use the US PrePress
Defaults color setting. In that case, when you first open the RGB scan,
naturally, what you're seeing is the RGB colors temporarily interpreted as
AdobeRGB, so your colors could very well blown out all the way to
the end of the spectrum, just because of the numerical mapping going
on inside
Photoshop from AdobeRGB to your monitor. As sRGB primaries are much
less saturated than AdobeRGB's (an often criticized shortcoming),
when you manually assign the sRGB profile to your image through the
Image>Mode>Assign command, all the colors "seem" to become more
"natural" looking.
Okay, like many things in color management, this sounds almost
understandable. ;-) Thanks!
Jack Clark
UC Davis
> Concerning the Assign Profile command in PS7, I observed this
interesting effect yesterday.
A local service bureau did some sample scans of a group of mounted
slides for me on their Scitex Jazz Plus. The scans were 8 bit, 20MB
each, with very little adjustment done in the scanning interface
software. I asked them to just make sure the important whites were
not blown out. Because the service bureau only had the lowest level
Scitex software for this scanner, no ICC workflow was used, and the
scans were delivered to me as untagged TIFF files (we were shopping
for a rate on bulk scanning).
During the course of evaluating the scans I discovered that, right
after opening the TIFF in Photoshop, if I use the Assign Profile
command to assign the loathsome sRGB profile to the file, there is a
dramatic, marked improvement in the overall image being displayed on
my monitor. It's similar to the dramatic change I see when sRGB is
assigned to untagged digicam images.
What's going on here? If I assign sRGB to these scans, which fixes
a lot of oversaturated colors real quick, then convert to Adobe RGB ,
then finish the editing and save, am I doing serious damage to the
file? Or, if I just assign Adobe RGB and then edit the glowing red
faces and other oversaturated colors, etc., which takes more time, am
I doing less damage than the sRGB route above. Finally, perhaps the
dumbest question of all, did Scitex create a scanner or scanning
software that scans into the sRGB space whether you want it or not?
I realize that the newer scanners for Creo are now much more
sympathetic to the ICC /RGB workflow.
Jack Clark
UC Davis
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