Re: sRGB & Jazz
Re: sRGB & Jazz
- Subject: Re: sRGB & Jazz
- From: Roger Breton <email@hidden>
- Date: Thu, 22 May 2003 12:27:52 -0400
Jack,
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.
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.
That's my take.
Roger Breton
Laval, Canada
email@hidden
>
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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| References: | |
| | >sRGB & Jazz (From: Jack Kelly Clark <email@hidden>) |