Re: CMYK files
Re: CMYK files
- Subject: Re: CMYK files
- From: Henrik Holmegaard <email@hidden>
- Date: Sun, 18 Feb 2001 23:09:31 +0100
If you know the source of the CMYK, the conversions will be a lot easier and
more accurate. With untagged files, it's a guessing game. Some suggest doing
a conversion to LAB but I'd have to believe that Photoshop would need to
make the same assumptions about the source to get to LAB so you may be in
the same boat.
To CIELab or further back to an RGB or CMYK space - the choice
depends on what tools are being used and what the workflow is meant
to achieve. Any device independent conversion references an
intermediate CIE space, CIELab or CIEXYZ for the ICC framework and
CIEXYZ for the PostScript framework. But the point is that there's a
choice.
An ICC profile carries within it the connection between the real
colors of the intermediate reference space, CIELab or CIEXYZ, and the
values that will reproduce those colors on the device, be it RGB
channel values, CMYK channel values, or K channel values. If there
are RGB or CMYK channel values with no embedded reference to CIE in
the data, then that data is color blind.
This use of an intermediate reference space gives a tremendous
flexibility. I can convert from device colors back to the
intermediate reference space, CIELab. I can convert from device
colors back via CIELab to my choice of synthetic RGB space such as
ECI RGB or Adobe RGB. Or I can convert from device colors back via
CIELab to another CMYK color space.
--
Henrik Holmegaard
TechWrite, Denmark