At 11:43 AM 5/22/2005, Jan-Peter Homann wrote:
Actually, I´m testing high-end solutions for doing CMYK2CMYK conversion.
Great.
Can you give us some idea of what software you are currently
testing? Images only? PDF or PS conversion? etc...
Preserving the black channel or better named "preserve original
separations" is a substantial step forward in the quality of CMYK2CMYK
colortransformations.
I see Preserve Original Separations as covering not only
preservation of black, but also of all four channels. In software such as
PDF Enhancer or CMYK Optimizer, you can see these options as "Preserve Ink
Purity" (where CMYK values with either single or dual ink usages are
maintained through the conversion).
It is necessary to understand, that preserving the original seprations is
different from preserving pure gray.
Agreed.
Gray handling, however, gets more complex not just as you discuss
but also when considering colors beyond simple CMYK - and in both composite
and separated workflows. Also, when looking at things such as "rich black
shadows" in a raster image, the maintaining/handling of the black becomes
significant.
We've done a lot of work on developing a technology we call "Gray
Reduction", where colors that are "gray", described in any supported
colorspace within PDF/PS can be converted into one of three standard forms
- DeviceGray, DeviceCMYK or "Spot Black". The reason for three options is
that each has validity in different workflows, depending on the downstream
tools/process. We've even taken this a step further when dealing with
raster images and attempting to maintain those rich shadows.
only colors with CMY=0 (pure gray) stay the same or changed only by a
1-Bit LUT / gradation curve.
In most cases, that isn't even true with most existing profiles in
use today :(.
The normal implementation in high-end applications for graphic arts is not
direct into the CMM, but in solutions for creation of devicelink-profiles.
Or at least use of DeviceLink profiles.
The problem, today, is that there are only a few tools that offer
to help created DL profiles and they seem to be mostly Mac OS X based. In
addition, very few applications that offer color management features
support DL profiles. So we end up with a bit of Catch-22 in trying to get
this excellent technology into user's hands.
Leonard
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Leonard Rosenthol <mailto:[EMAIL PROTECTED]>
Chief Technical Officer <http://www.pdfsages.com>
PDF Sages, Inc. 215-938-7080 (voice)
215-938-0880 (fax)
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