Re: Perceptual Javex
Re: Perceptual Javex
- Subject: Re: Perceptual Javex
- From: "eugene appert" <email@hidden>
- Date: Thu, 21 Sep 2006 16:37:06 -0400
"Is it a matrix profile, an XYZ PCS Lut profile,
or a L*a*b* PCS Lut profile ?"
Graeme,
Thanks for your answer. According to Colorthink this profile is a16 bit, 25
grid point table based profile, L*a*b* PCS Lut. Colothink also describes
it as a scnr type, I am not sure what that means. Though it shows a white
and black point of L*0 and L*100 in the devise color space area , it
describes the PSC white point as 0,9462, 1,,08249 in ICC technical
attributes. However under the tag table tab, it describes the media white
point as:
XYZ: 0.9640808, 0.9999847, 0.8248901
Lab: 100,, -0,03, 0,02
LCH: 100, 0.04, 154.72°
Yxy: 1, 0.35, 0.36
Luv: 100, 0.21, 0.49
5000°K
It seems strange to me that the media white point, in this case created by
an Epson 4900 scanner from an IT8 on Ektachrome 4x5 transparency film would
produce exactly 5000k and despite the reference target value of L*88 in the
GS 0 (or minimum density patch) produces L*100 as a media white point.
And since as you say ,....
"Note that the standard way profiling input devices operate, is that the
white point of relative colorimetric rendering will be taken from the white
patch of the profiling target."
It makes me think that this is an indication of error, perhaps the problem
you mention with some profiling software outside the target range. Would
this mean that the dynamic range of the scanner exceeds the expected
response by the profiling software for the white patch. Such that any white
patch value measured above L*88 would be shot to L*100 and the profile
cannot process values between the two?
Thanks
Eugene Appert
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