Re: colorsync-users digest, Vol 3 #985 - 10 msgs
Re: colorsync-users digest, Vol 3 #985 - 10 msgs
- Subject: Re: colorsync-users digest, Vol 3 #985 - 10 msgs
- From: Don Hutcheson <email@hidden>
- Date: Sat, 27 Sep 2003 08:46:26 -0400
On 03/09/27 1:00 "Broudy, David" <email@hidden> wrote:
>
What profiling apps support direct creation of gray output profiles?
>
Profilemaker Pro lets me save a previously-created CMYK output profile as
>
gray, but I think all that does is copy the K dotgain info. this doesn't
>
account for using a book-black ink which has different repro characteristics
>
from process black, and if it is saving more than the dotgain info such as
>
L*, it's probably wrong for my needs.
>
>
basically I want a profile to use for converting RGB and CMYK images to
>
grayscale while applying a subtle contrast curve to alleviate the usual flat
>
appearance of a generic conversion. I have one that I made in Linocolor 6,
>
but it has some compatibility issues with a few apps and I'd rather use
>
something a little less ancient than LC6.
>
David,
If you already have a CMYK profile for your device, there is little need for
a separate grayscale profile. Just select your CMYK profile via the 'Load
Gray ...' item at the top of the Gray: Working Space list. Photoshop quickly
runs a few K-only dot percent samples through the forward tag (Device CMYK -
to - PCS) of your CMYK profile to find the equivalent L* values, then
inverts those samples to form a L* - to - K% LUT, which constitutes a gray
profile! Simple but clever.
Note that the name in the Gray: Working Space field becomes "Black ink -
(your profile name)" and you can also export a Gray profile of the same
name, which appears to be nothing but a 1-D ramp.
When you select 'Image - Mode - Grayscale', the resulting grayscale file
should allow for the black-only print characteristic curve of your device,
and produce virtually the same tonal accuracy as a 4-color B&W image, minus
the extra bit of shadow density that would have been contributed by CMY.
For more control over rendering intent you can select 'Image - Mode -
Convert to Profile - (grayscale profile name).
The only two potential weaknesses with this process that I can see are;
1. Most profiling targets don't contain very many black-only patches, so
the accuracy of the 1-D LUT may be less than perfect. If you don't like the
tonal accuracy of your black-only prints, you can edit the FORWARD TAG of
the profile with a 1-D Black channel adjustment, but I seldom find that
necessary. It seems Adobe do some intelligent interpolation, at least on the
gray profiles I've created.
2. You don't have control over the Maximum K percentage value. Usually
you'll find some pretty high numbers like 99%, which in rare cases may be a
problem on certain substrates, like newsprint. But in practice I find these
images print very well on most devices.
I hope this helps.
Don
******************************
Don Hutcheson
Hutcheson Consulting
(Color Management Solutions)
E-mail: email@hidden
******************************
_______________________________________________
colorsync-users mailing list | email@hidden
Help/Unsubscribe/Archives:
http://www.lists.apple.com/mailman/listinfo/colorsync-users
Do not post admin requests to the list. They will be ignored.