[argyllcms] Re: 0.60 CMYK profile misshaped

  • From: Graeme Gill <graeme@xxxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Tue, 12 Dec 2006 15:49:01 +1100

Roberto Michelena wrote:
> the real problem is determining the ink limits automatically.

I'm not sure any automatic system can work based purely
on measurement, at least when dealing with the underlying
raw channel behaviour. For instance, the actual dot coverage
will depend on the resolution an inkjet is being run at,
so 100% channel value may correspond to an actual 200%, 400%
or more ink coverage. On the Colorbus RIP we had a gross
scale factor that had to be set, and then the more
fine grained per channel limit (set by the density aim target)
could be determined more automatically. The gross limit was
determined by looking at things like "was the ink running off
the page". There were additional magic numbers that needed to
be set which determined light ink separation etc.

shape (for example, target being ISOCoated). Then I can clearly see,
by rotating the graph and looking at it, which limits do I have to set
in each ink channel to be able to encompass the target gamut. I can go
that much, or higher; but not lower.

I would guess there are different aims for setting ink limits.
If you have a particular gamut as a target, then you might find
there is no need to push beyond what you need, or you might find
that you have to push beyond the natural limit to be able to
cover the gamut. On the other hand if you're just making pretty
pictures, you'll probably aim for a comfortable limit.

Graeme Gill.


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