Re: device link profiles / reprosauria revisited
Re: device link profiles / reprosauria revisited
- Subject: Re: device link profiles / reprosauria revisited
- From: Henrik Holmegaard <email@hidden>
- Date: Wed, 31 Jan 2001 09:08:31 +0100
"Broudy, David" <email@hidden> wrote:
what is 1) the definition of and 2) the practical uses for, a device link
profile, and why would I need one?
I think the short, sweet and snappy definition of device link
profiles is 'a legacy idea' ... -:)
Look at it this way: If you forge Space A and Space B permanently
together, Space A always knows its going to Space B and Space B
always knows its getting the gamut of Space A. If you use device
profiles, then Space A can't know anything whatsoever about the space
it will be converted into nor can Space B know anything about the
gamut of spaces you will convert from. This leads to the idea that
device link profiles are a great idea because you can tune the gamut
mapping whereas with device link profiles the destination space must
have a strategy for gamut remapping for the whole of the profiling
software's internal Lab gamut (which is not the whole of Lab as Lab
is unbounded and hence not an object).
What this argument forgets is that links are totally color blind. A
device link is a one way street. It converts from Color Space A into
Color Space B, but once the data is in Color Space B there is no
definition of how to get the colors back into CIELab / CIEXYZ and
therefore no repurposing / simulation capability. The ICC
specification also forbids embedding of device link profiles.
And if you wish to use device link profiles to color manage
multi-object and multi-color space transport file types such as PDF
or PostScript, all your device links must end in the same color space
(typically 'MyProofer.ICC'). The way device link profiles are built
you have no way of documenting them. It doesn't help me to know that
the source is 'CMYK data color space' and the destination is 'CMYK
data color space'. I want to know exactly what was the name and
creation data of the original CMYK1 profile and CMYK2 profile.
Otherwise I have no idea what I'm matching.
The problem here is that links are a relic of the age of reprosauria,
the great old CEPS closed product lines of the eighties and nineties.
Nobody wanted to repurpose anything and nobody wanted
interoperability and modularity in color space transforms.
You can use links, and if you take care when matching then you may
get good results, but you should only use them when matching into
final output with no idea of repurposing the file later on. Or you
should set up a separate tagging task after the match that embeds the
device profile for the color space you matched into, if you know
because you remembered to write the source and destination space
names into the Finder/Explorer and description tag of the device link
profile -:).
--
Henrik Holmegaard
TechWrite, Denmark