Re: Lab is always "just right" (was Hexachrome Scanning)
Re: Lab is always "just right" (was Hexachrome Scanning)
- Subject: Re: Lab is always "just right" (was Hexachrome Scanning)
- From: "Vanderlinden, Thomas M." <email@hidden>
- Date: Mon, 10 Sep 2001 12:48:00 -0400
good morning, all - - - -
Thanks to Neil Barstow for the reminder
that conversions to a color space are colorimetric.
I have been reading those discussions pretty closely
and even made note of it, but I guess
it's just not yet a part of me.
I should have said:
"doesn't this mean that when a file is converted
from the scanner RGB into Lab that the reds in that wing
are shifted to be inside the boundary of the Lab space?"
I like the idea of using ColorThink to answer this question
by mapping the image data in 3-D.
But I am not certain that this can be shown by that means.
The ColorThink manual, page 37, reads:
"Image Inspector will convert all image colors to Lab
using the embedded profile and send them to the graphing tool
for display. ...The absolute colorimetric rendering intent
is used to convert from RGB to Lab color.
If a different intent is desired, export to a color list, as above."
So, if I understand this correctly, if there are reds that I'm capturing
in that red wing of my scanner space, I can't tell from the 3-D Grapher
because they have already been shifted into the Lab space
is order to be graphed.
So the question remains. Am I capturing reds that are not surviving
the conversion to Lab?
Neil's question:
>
"And do we know that the PCS is only as big as Lab?"
, I believe focuses on my comment:
>
When I view with the 3-D Grapher a Lab profile gamut
>
overlaid with other color spaces I work in,
>
I notice that the Lab space does not completely enclose them.
>
The reds of Adobe RGB (1998), EktaSpace PS 5, J. Holmes,
>
my custom scanner RGB profile, my custom ink jet profile.
I do not know the answer. Is the PCS only as big as Lab?
Why does even a modest (reflective, not transparencies) scanner
profile appear to enclose a larger space than Lab?
I don't know.
Or, in the spirit of recent good advice,
perhaps I should instead ask: what am I assuming here
that perhaps I should not be assuming?
- - - Tom Vanderlinden
email@hidden
Bridgeport National Bindery