[argyllcms] Re: V1.1.0 Perseptual rending Qst
- From: Graeme Gill <graeme@xxxxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Wed, 20 Jan 2010 12:22:47 +1100
Wallden Magnus wrote:
I did a printer profilling vhit V110, see below.
When using Perseptual rending the black and dark grey, below aprox RGB
10,10,10 turned into a nice blue color,
mostly like a "shadow warning"
If Relativ or Absolut rending this dont happend, now it is dark
grey-black.
Hi,
the measurement values for the device seem rather strange.
For instance:
SAMPLE_ID CMYK_C CMYK_M CMYK_Y CMYK_K XYZ_X XYZ_Y XYZ_Z
515 100.00 100.00 100.00 0.0000 -1.0366 -1.5231e-006 -0.23692
A Y value of 0.0 would be highly unusual, a value less than 0.0
is truly miraculous !
Since you seem to be using scanin, I'm presuming you are using
a calibrated scanner as a substitute for an instrument. I would
guess that the test chart is exceeding the range over which the
scanner is profiled (ie. the scanner reference chart has insufficient
dynamic range), and that the resulting extrapolation
is resulting in unrealistic values near black. (I'd
need the necessary files for the scanin step to check
exactly what's happening though.) (Perhaps you're using a matrix
profile for the scanner where a cLUT profile would give better accuracy ?)
If this is what's going on, It's no surprise that the profile behavior
near black isn't very accurate.
Graeme Gill.
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