Re: Inkjet profiling ABC
Re: Inkjet profiling ABC
- Subject: Re: Inkjet profiling ABC
- From: Henrik Holmegaard <email@hidden>
- Date: Thu, 15 Nov 2001 09:52:14 +0100
OK...so how does one not apply ink limiting to one's targets?
Wrong way round -:)
Calibration is broadly speaking the process of bringing your setup
into an optimal and repeatable state. When that state is reached, you
feed a test chart like so,
a. scanner: capture IT8 or Eye-One reflective target for which you
make sure the RGB capture is not pixel converted in Pshop or
LinoColor or ... ,
b. monitor: Eye-One or ProfileMaker software flashes chart patches on
monitor automatically and you can't accidentally convert the values
through color management,
c. printer: you Place / Open an Eye-One or ProfileMaker CMYK test
chart in Quark / InDesign / Photoshop, switch off color management in
the application and in the RIP, print, allow for dry-down, and
measure.
Ink limiting preferably occurs before the test chart is fed. Say on a
press you determine the ink densities before feeding the test chart.
On an inkjet you either manually pull curves to set the ink densities
as in the BEST RIP or the ink densities are stored as preset curves
in the RIP as in the HP DesignJet RIPs, and only then do you feed the
test chart. In both cases the ink limiting is (: should be) distinct
from the color management system. Say in HP DesignJets the ink limit
preset is independent of PostScript color management and ICC color
management.
But if no ink limiting is applied before the test chart with its 400%
CMYK values is fed to the RIP, you will not get a good result. The
test chart can only record the gamut size and shape you print, and
you can only measure what you print, too. So optimize the ink
limiting in the RIP, then print the test chart and measure up for
your profile. Then choose the Eye-One or ProfileMaker 'Inkjet 400%'
preset (or customize the separation in ProfileMaker, if you wish).
Note that if you send a CMYK RIP an RGB test chart, the RIP will use
the Level 1 device RGB to device CMYK transform which includes curves
for black replacement. Though you will be able to capture the full
gamut (as far as I recall), you are better off feeding a device CMYK
test chart to a CMYK RIP.