[argyllcms] Re: conjgrad failed

Mickael Profeta wrote: 
Yet, it does not totally work, dispcal fails to create the calibration
file. I detect two strange things: the target black got a nan value and
it fails with a conjgrad error:

:~/test32/bin$ ./dispcal -i92 -a ../log/test
Offset calibration:
Place instrument on a dark surface.
Hit Esc to skip, any other key to start calibration:
Offset calibration successful
The instrument can be removed from the dark surface.
Cell ratio calibration:
Place instrument on test window.
Hit Esc to skip, any other key to start calibration:
Cell ratio calibration successful
The instrument can be removed from the screen.
Place instrument on test window.
Hit Esc to give up, any other key to continue:

Press 1 .. 7
1) Black level (CRT: Brightness)
2) White point (Color temperature, R,G,B, Gain)
3) White level (CRT: Contrast, LCD: Brightness)
4) Black point (R,G,B, Offset)
5) Check all
6) Continue on to calibration
7) Exit
Doing some initial measurements

Adjust CRT brightness to get target level. Press space when done.
   Target 0.45
\ Current 0.00  +


This is a rather unusual value for black. You performed a calibration,
so are you sure you performed it correctly ? At the first step of
the calibration, did you place the instrument on completely black surface,
and in a dark place (ie. something opaque over the instrument), or did
you accidentally have it on the screen at the time ?
Doing the latter will cause the screen black to read 0.0, or even
-ve, possibly causing the numerical errors that follow.

Graeme Gill.


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