[argyllcms] Re: some questions for using targen

  • From: Graeme Gill <graeme@xxxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Wed, 29 Sep 2010 10:45:31 +1000

Michael Schulz wrote:
Thank you for the explanation! Novice question: How should I decide the ink
limit? The printer is already ink limited by the rip/linearization. So far
I've chosen 400% ink limit creating the profile. Should the targets (A or B)
be printed with the ink limit given by the rip?


It's not ideal that the ink limit be imposed outside the profiling. As indicated
in the tutorial guide, it is desirable that the test chart have an ink limit
slightly larger than the one finally imposed in making the profile.

So ideally you should set the RIP ink limit to be 10% higher than the
one you ultimately choose, and use that 10% higher limit with targen,
and to print the test chart. You should then use the original ink limit
in making the profile (which by default will be 10% lower than that
used by targen.)

Choosing an ink limit is something of an art. There are some hints at the
bottom of <http://www.argyllcms.com/doc/Scenarios.html#PP6>.
Basically it's a trade-off between depth of black and other practical
considerations, such as wetness, smudging, spreading, drying time and ink
consumption. (On the to-do list is to come up with a test chart suitable
for judging ink limits.)

If you do not want to alter the RIP, then you can try running with 400% ink
limits, but it's less certain how well it will work. Having an ink limit
imposed outside the profiling path essentially collapses the device gamut,
and this could conceivably lead to strange results when computing the B2A
tables (even though the code tries to avoid such problems).

Another issue is that there can be more than one way of computing
the ink limit, so different programs may not be computing it in quite
the same way (e.g. see <http://www.argyllcms.com/doc/Scenarios.html#PC6>
for an example).

Graeme Gill.

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