RE: Dry Time for UltraChrome inks/Calibration
RE: Dry Time for UltraChrome inks/Calibration
- Subject: RE: Dry Time for UltraChrome inks/Calibration
- From: Ray Maxwell <email@hidden>
- Date: Mon, 3 Feb 2003 10:58:30 -0800
Damon Wrote:
>
I've found that the key in profiling UltraChrome based prints is proper
>
calibration (linearization). There is density reversal in all four inks
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as is commonly found. Effective maximum density (just before density
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reversal) occurs at about 75% (uncalibrated dot area) depending on ink
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and media. There is a very significant saturation reversal and hue
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shift at about 60% (depends on paper) for both magenta and cyan. It is
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important to limit the ink before this reversal takes place. Not doing
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this makes prediction of secondary colors difficult for profiling
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software. This can be seen in the Hex plot of a profile created without
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significant cut back. This cut back also does not significantly effect
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the gamut of the profile. The additional density doesn't contribute
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significantly to color saturation.
>
>
This is not real easy to explain in a short paragraph. It is best
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demonstrated with pictures. At some point I will post all of my
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findings on a web page. I'll send you a separate email with screen
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grabs of these 3D plots. I'm happy to send this to anyone on the list
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that is interested.
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>
Regards,
>
>
Damon
>
I agree with everything you have said and would add the following:
When setting ink limits I always do a spider diagram in Lab space of the CMY
inks and look for the maximum chroma point.
Many ink and paper combinations actually hook back. By this I mean that as
you increase density they will hit a max. chroma and then shift in hue and
reduce in chroma. Setting ink limits above this point does not increase the
gamut and gives your profiling package allot of trouble.
I suggest that you look at a spider Lab plot and not just density when
setting ink limits.
Ray Maxwell
P.S. A spider Lab plot is just a plot of a* and b* values made from a
density step wedge of each color.
Creo
Ray Maxwell | Senior Color Systems Engineer, Inkjet Printing
4225 Kincaid Street | Phone (604) 451-2700 ext. 2004
Burnaby, B.C.
Canada V5G 4P5
IMAGINE CREATE BELIEVE
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