Re: LAB to a printer vs. RGB or CMYK?
Re: LAB to a printer vs. RGB or CMYK?
- Subject: Re: LAB to a printer vs. RGB or CMYK?
- From: Graeme Gill <email@hidden>
- Date: Mon, 23 Jan 2006 11:40:27 +1100
t labarbera wrote:
Does anyone think it would be a good idea to send LAB files for print production rather than what
I take as the norm of some flavor of RGB (perhaps with an embedded profile) or CMYK.
One of the subtle issues at the moment with using LAB as a raster encoding format,
is that most current tools and workflows are set up to assume colorspace gamuts (i.e.
that images encoded in a particular colorspace are rendered (optimized) for that
colorspace, and that therefore the gamut of the colorspace can be assumed to represent
that of the images, and should be the one to use as the source during a colorspace
conversion.)
When you supply images encoded as LAB, there can be no such assumption, since
LAB doesn't have a gamut (not one that means anything, anyway.)
Given a set of images encoded as LAB, and the task of converting them to
CMYK, there are two possible conversion assumptions:
1) Make an assumption about the gamut of the images, ie. that they
are really sRGB gamut, or perhaps SWOP ? - random choice really,
and then convert to CMYK on the basis of that.
2) Build a gamut from the image content, and then use that as the basis
for colorspace conversion. Should each image be processed separately,
or should a combined gamut be used for the whole job ? - who knows.
Either way the exact color reproduction is not likely to be consistent,
which could be both an advantage (the color conversions are more optimized),
or a problem (if you want the gamut mapping to be consistent between images or
jobs.)
Either way, few of the color conversion toolsets are set up to really deal with
the above issues, and you have left a lot of things unspecified.
The technical solutions (as I see them), are:
1) Color toolsets need to have the facilities to deal with such issues.
2) LAB (and other device independent colorspace encodings) need to
have the facility to embed a gamut description along with the image(s).
Graeme Gill.
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