Monitor RGB should be the smallest color gamut I believe, and so it must have the maximum gamut issue. Instead here I notice the gamut warning is grayed out. This is counter intuitive to me.
Photoshop Manual says:
"All pixels outside the gamut of the current proof profile space are highlighted in gray."
Using a scanned slide in 16bit with embedded profile proPhotoRGB, produces warnings when Soft Proof is set to CMYK, but when set to MonitorRGB, the options jsut goes away (grays out!).
this is for CS6.
Soft proofing for Monitor Profile can be done by two different methods:
A) View > Proof Setup > Monitor RGB
In this case Gamut Warning is not available.
B) View > Proof Setup > Custom
Custom > Monitor RGB (Profile) by name, as below
Preserve RGB Numbers unchecked
In this case Gamut Warning can be activated.
Illustration, please use zoom=100%:
MP: Monitor Profile, direction XYZ --> RGB
MP': Inverse Monitor Profile, direction RGB ---> XYZ
XYZ: Profile Connection Space CIE(1931) XYZ
Measured Monitor Profiles are mostly not Matrix Profiles but Table
based Profiles. In this case the Profile Connection Space is Lab.
MP: Monitor Profile, direction Lab --> RGB
MP': Inverse Monitor Profile, direction RGB ---> Lab
Lab: Profile Connection Space CIELab
In color managed applications in Photoshop MP is applied in advance to
sending data to the graphics card VRAM.
A) Soft Proofing by Monitor RGB works without any color management.
RGB values are sent directly to the graphics card VRAM and from
there via LUTs (Look-up-tables) to the monitor.
MP is not used.
B) Soft proofing by Monitor Profile generates the sequence MP'·MP
The product MP'·MP is explicitly executed. In this case one can
compare the input of MP' and the output of MP. In any case of
clipping these values are different (beyond ordinary numerical inaccu-
racy) and the respective pixel can be marked by an alarm color
(here Magenta) as a Gamut Warning.
All tests by PhS CS2. Corrections and comments are appreciated.
Best regards -- Gernot Hoffmann.
Message was edited by: G.Hoffmann