Question on Scanning and Gamuts

[Chris Stolpe]

Why doesn't a scanner scan the widest gamut and convert it to the target
colorspace the same way as the editing software?
My monitor is calibrated for sRGB and I believe both photoshop and the
scanning software translate the scanned colorspace to my monitors sRGB
colorspace as best it can. What I don't understand is why it appears that
the shadow areas when scanned in Adobe RGB 1998 colorspace are brighter than
sRGB and Scanner RGB is even brighter than Adobe RGB 1998. It looks like the
wider the gamut the more dynamic range you have. If that dynamic range was
there why doesn't it show up in a sRGB scan.? The scanner software and Adobe
Photoshop are both able to convert it to my monitors sRGB colorspace and
retain that brightness in the shadows. So why is that the shadow brightness
is lost if I scan in sRGB? Either way when I view these scans the software
has to translate them to my monitors sRGB. It also looks to me that the
Adobe RGB 1998 scan has a greenish cast and the Scanner RGB is warmer. I
don't like the greenish cast.

I did a screenshot of the three scans:
http://photos.yahoo.com/[email protected]
Left is Scanner RGB
Middle is sRGB
Right is Adobe 1998 RGB

TIA
Chris

 

[Roy]

Why doesn't a scanner scan the widest gamut and convert it to the target
colorspace the same way as the editing software?
My monitor is calibrated for sRGB and I believe both photoshop and the
scanning software translate the scanned colorspace to my monitors sRGB
colorspace as best it can. What I don't understand is why it appears that
the shadow areas when scanned in Adobe RGB 1998 colorspace are brighter
than sRGB and Scanner RGB is even brighter than Adobe RGB 1998. It looks
like the wider the gamut the more dynamic range you have. If that dynamic
range was there why doesn't it show up in a sRGB scan.? The scanner
software and Adobe Photoshop are both able to convert it to my monitors
sRGB colorspace and retain that brightness in the shadows. So why is that
the shadow brightness is lost if I scan in sRGB? Either way when I view
these scans the software has to translate them to my monitors sRGB. It
also looks to me that the Adobe RGB 1998 scan has a greenish cast and the
Scanner RGB is warmer. I don't like the greenish cast.

I did a screenshot of the three scans:
http://photos.yahoo.com/[email protected]
Left is Scanner RGB
Middle is sRGB
Right is Adobe 1998 RGB

TIA
Chris

A profile for a Calibrated Monitor is not a sRGB profile.

It is a Device Profile, specifically a monitor profile, which converts the
numbers for colours in your Program's Working Space to give you correct
colour on your screen. The numbers being used in the Working Space remain as
they were, it only changes the numbers which will be sent to the Monitor.

SRGB, Adobe RGB, Pro Photo RGB, etc are Working Space Profiles, which Photo
Programs use to make the alterations to the numbers for colours, when you do
manipulation. Working Spaces are, by definition, Device Independent.

If you have chosen Adobe RGB as your Working Space, then you should be
getting your Scanner to output to Adobe RGB via your scanners Colour
Management system, which will use your Scanner Profile to make the necessary
conversions.

However many people prefer to set their scanners to No Colour Management,
and then Assign or Convert to the Working Space Profile in their Photo
Program. But that is a bit of an advanced technique.

You will have a number of Device Profiles on your system, Scanner Profiles
and Printer Profiles as well as the Monitor Profile.

I think you should spend a little time reading up on colour management, and
the use of these profiles, because as you now notice, your workflow is
causing some problems.

It is not easy, but it is not rocket science either.

Have a look at

 

[Roy]

Why doesn't a scanner scan the widest gamut and convert it to the target
colorspace the same way as the editing software?
My monitor is calibrated for sRGB and I believe both photoshop and the
scanning software translate the scanned colorspace to my monitors sRGB
colorspace as best it can. What I don't understand is why it appears that
the shadow areas when scanned in Adobe RGB 1998 colorspace are brighter
than sRGB and Scanner RGB is even brighter than Adobe RGB 1998. It looks
like the wider the gamut the more dynamic range you have. If that dynamic
range was there why doesn't it show up in a sRGB scan.? The scanner
software and Adobe Photoshop are both able to convert it to my monitors
sRGB colorspace and retain that brightness in the shadows. So why is that
the shadow brightness is lost if I scan in sRGB? Either way when I view
these scans the software has to translate them to my monitors sRGB. It
also looks to me that the Adobe RGB 1998 scan has a greenish cast and the
Scanner RGB is warmer. I don't like the greenish cast.

I did a screenshot of the three scans:
http://photos.yahoo.com/[email protected]
Left is Scanner RGB
Middle is sRGB
Right is Adobe 1998 RGB

TIA
Chris

Sorry, pressed the wrong button by mistake.

As I was about to say, have a look at :-
www.computer-darkroom.com

There is lots of reading there.

Roy G