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Re: Matchlock Cyan Skies



<x-charset iso-8859-1>Bob,

Thanks for that explanation, it's finally made the problem with
scanner based profiling clear to me.  My Agfa T-2500 software does
allow specing the source space, and here the profiles are *much*
better than with any other setting.  Profiles made any other way
suffer from inaccuracies, cyan skies being the most serious and
offensive of the color problems.

Dave

----- Original Message -----
From: Bob Smith <bobsmith@mac.com>
To: <epson-inkjet@leben.com>
Sent: Wednesday, October 25, 2000 8:11 AM
Subject: Re: Matchlock Cyan Skies


> David Corwin wrote:
>
> > Yes, I've tamed the cyan skies as well by adding red, but it seems
a rather
> > bass-ackwards way of doing things.  My best results come from
avoiding
> > out-of-gamut blues, but that isn't always possible.
>
> The scheme used by profile creation software to move out of gamut
colors
> into gamut in a perceptual transform; is generally one of the key
elements
> that differentiates various profiling packages.  There is no one
correct way
> to do it.  The results are highly subjective and vary with different
> packages.
>
> For one thing, the conversion process itself does not look at the
source
> space when figuring out how to compress colors into the output
space.  It
> uses the same compression scheme (which is part of the output
profile)
> whether the source is a huge space or a tiny one.  When the profile
is
> created the software package makes assumptions about the type of
space that
> would typically be used for the source.  There are only a couple of
packages
> that let you specify your typical source space when the profile is
built.
>
> The bottom line is that the results you get from a perceptual
conversion may
> or may not fall in line with your expectations.  To get different
results
> you need to either:
>
> create the profile using different settings in the profile
generation
> software, or a different profiling package.
>
> edit the perceptual table of your profile to get results more in
line with
> your expectations.
>
> use Photoshop's preview functions and gamut warning as you move the
most
> critical if not all colors into gamut before conversion.
>
> or edit the file after conversion to output space to yield the
desired
> results.
>
> Deep blues seem to be the area that frequently cause problems.  I
believe
> this is because a simple straight desaturation to move some of those
colors
> into gamut causes us to perceive a shift in hue as well.  Colors in
the
> range usually need hue shift as well as saturation change to produce
> pleasing results.  Figuring out what's best for you is highly
subjective.
> Consider yourself lucky if your profiling package nails it perfectly
on the
> first try.
>
> Bob Smith

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