Hi William
3/10/03 7:00 pm William Chitham <will-at-black-door.co.uk> wrote
>Dear List,
>
>Can anyone enlighten me a little about how Photoshop uses a profile when
>soft proofing? Am I right in thinking that when you make a profile there is
>the part that makes the necessary colour corrections for accurate output and
>then another part which describes the characteristics of the
>printer/ink/paper combination in terms of gamut, D Max, paper white colour
>etc?
it's not quite like that, the part that makes the necessary colour
corrections for accurate output uses the data [which describes the
characteristics of the printer/ink/paper combination in terms of gamut,
D Max, paper white colour etc. ] to do that.
When we measure charts (in making a printer profile) the Lab values of
the printed patches are recorded and compared to the RGB data from the
chart, this provides the A>B tag, which is used to convert data in
printer space to Lab. This is the tag used for softproofing.
The B>A tag which we use when actually converting data in preparation
to make a print [or on the fly during printing] is made by calculation
from the A>B measurements.
In simplified terms - when we softproof we use the B>A to effectively
convert the data to print space, then the A>B to convert it to Lab,
then the monitor profile to cobvert from Lab to monitor space - so we
can view it.
Amazing it's done so fast isn't it.
>I've been making profiles with Eye 1 match which look pretty dreadful
>when soft proofed but print fairly well whereas a profile I made with the
>Fuji ColorKit looked great as a softproof but produced a diabolical print.
sounds as if something's broken.
Regards, NeilB. Apple Solutions Expert
colourmanagement.net :: Consulting in Imaging & Colour Management
custom scanner and printer profiles, training on Imacon Scanning
supply Gretag + eyeOne, ColorSoloutions basICColor : Display etc. XRite
www.colourmanagement.net/ :: www.apple.com/uk/creative/neilbarstow/
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