Re: Printer Profiling Issues
Re: Printer Profiling Issues
- Subject: Re: Printer Profiling Issues
- From: Scott Martin via colorsync-users <email@hidden>
- Date: Tue, 25 Jun 2019 15:53:19 -0500
Well said Don!
Randy, I think there are two different ways of responding to this. One is to
talk about how we optimize the pre-profiling calibration steps (ink
restrictions, linearization, and total ink limits). Another is to talk about
your target and ∆E calculations.
Let’s start with this 24 patch "Randy Chart". What is the intent of this
procedure? Are you hoping to optimize Pantone color reproduction or something
similar? Are you trying to evaluation your calibration and profiling
procedures? Artwork reproduction?
How were the values created? How are you printing the target? Are you expecting
the printed values to match the reference values in the digital file? Are the
∆E values you're generating comparing the reference values to the printed
values, or something else?
If you make a TIFF file with values like:
White L=100 a=0 b=0
Black L=0 a=0 b=0
Red L=60 a=128 b=100
No print will ever hit these values regardless of what rendering intent or
profiles we use. And it’s not fair to expect the prints to do it. And their
ability to get close to these values isn’t and indication of how good the
profile is.
White L=100 a=0 b=0 will become whatever the paper white of the media is.
Black L=0 a=0 b=0 will become whatever the Dmax of the process is.
Red L=60 a=128 b=100 will become roughly whatever the max red saturation is for
that process, and the different rendering intents might make it look quite
different if things like chroma darkening are employed for example.
That said, perhaps all of your patches fall well within the color gamut and
you’re printing with AbsolCol and hoping to hit the numbers in the file for
colorimetric accuracy as opposed to visual color matching or something else.
Either way I think we’d love to hear more about the Randy Chart and the intent
for this type of evaluation.
Scott Martin
www.on-sight.com <http://www.on-sight.com/>
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