Re: filmscanners: Vuescan: "device RGB"

["shAf" <michael@shaffer.net>]

Richard writes ...

> Yes it is large. It will encompass Ekta Space (almost), which is the
> definition of E6 Ektachrome media, and thus E6 gamut.

    I'm posting th results of my little test regarding the capacity of
Vuescan's gamut, "device RGB" (... whatever it is ...)

    First ... some prelims ... I scanned an image into sRGB space 1st
just for getting the colors approximately correct on my gamma=2.2
monitor ... and then loaded it into Photoshop 6.  Next ... I scanned
another image, without changing anything, into a wide gamut space,
ProphotoRGB (gamma=1.8) ... and loaded it into Photoshop.  Both of
these "appear" identical, so there is nothing wrong with my monitor
compensation.

    Second ... I scan having chosen "device RGB" which doesn't embed
any profile, but is supposed to be Vuescan's color space.  I can
choose to "assign" any profile to it, and the profile which makes it
appear like the others will give us an idea of "Vuescan RGB" color
space.  If I assign a profile and it appears over-saturated, then VS
RGB has a smaller gamut than what I assigned, and vice versa if it
appears under-saturated.

    The result is VS RGB is somewhere inbetween ProPhotoRGB and sRGB,
and most like EktaspaceRGB.  Unfortunately, VS RGB is a smaller gamut
than what Nikon believes belongs to the LS-2000 ... if I assign
"Nikon_wide" the over-saturation is obvious.  Fortunately, and as
Richard stated before (at least with respect to Nikons), the scanner's
gamut is designed to exceed that of the media ... so Ektaspace is an
easily accepted compromise.  Ektaspace is also respected for its
editabilty, and its wide gamut is very suitable for highbit editing.
Its gamut is also sufficiently wide for archiving.

    The downside of VS RGB, besides being smaller than some scanners'
device spaces, is that it is significantly smaller than "Adobe wide
gamut" and ProPhotoRGB.  That is, you get nothing by choosing these
two color space options ... unless you like a lot of headroom for
serious Photoshop adjustments ... but the "beyond gamut" results of
such adjustments cannot be seen in monitor space, so what's the use(?)

    The good news is VS RGB is sufficiently large.  No one should
complain for lack of gamut ... no matter what the application post
scan.  It is also sufficiently large for some serious and creative
highbit adjustments.  On the other hand, if Ed wanted to extend
Vuescan's market into professional work, he might want to consider a
different internal color space for Vuescan 'Pro'.

my US$0.02