Re: Profile Names (and output condition tag)
Re: Profile Names (and output condition tag)
- Subject: Re: Profile Names (and output condition tag)
- From: Graeme Gill <email@hidden>
- Date: Sun, 07 Jan 2007 10:44:33 +1100
Martin Orpen wrote:
On 6 Jan 2007, at 14:37, Graeme Gill wrote:
[I know the first tag on my list, would be a total ink limit tag.]
Do you need to use a tag for this, surely it can be calculated from the
profile data?
Purely on principle it's poor design not to have this information
explicit. It's a basic gamut limit of the color space, and
we shouldn't rely on a secondary artefact such as the B2A table
to guess what it is.
It can't be assumed that a B2A table accurately reflects the target
ink limit for a device, and it's slow to extract. An issue
is that the profile ink limit can only be accurately controlled
at the clut grid nodes, and the mixing behaviour within clut
cells is at the mercy of the CMM interpolation algorithm,
so examining a B2A table doesn't accurately tell you what the
target was, it just represents a sampling of it. Some device
behaviours may not cause any output values at the ink limit
either (ie. they reach maximum black at less than the target
ink limit).
For the type or workflows that are interesting to me ("active"
or "smart" CMM workflows), I don't want or need to generate
any detailed B2A tables in the profile, I just want detail
in the colorimetric A2B table, so its speeds things up and
saves profile space to create profiles with a very low resolution
B2A table. At the link stage, I need to be able to quickly
determine the ink limit of the source and destination profiles,
to establish their gamuts. It is clunky to have to carry this
information (established at the profile test chart creation stage)
"by hand" to the link step. Instead it should be carried automatically
through the workflow using the profile.
Graeme Gill.
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