Re: Screen profiling

Bob, Gernot, Graeme und Gerard,

To check that, I'm going to put my screen in a big white light box (1m x 1m
x 1m) lighted with 4 daylight flash tubes at each corner. Then I will be
able to see if the screen rendering and the printed patch looks similar for
a same given XYZ value.

I have been following the thread and I'd like to throw in my contribution.

I am using two LCD monitors, side by side. I calibrate each with the same
EyeOnePro to the same chromaticities (D50) at the same luminance (160). I
verify the calibration on both to be under 1 DeltaE.

Surround is well below 32 lux.

When I observe the grays on monitor A (while monitor B is closed) the
appearance of the grays on monitor A evokes a very neutral impression to my
visual system. When I observe the same grays on monitor B (after closing
monitor A) the appearance of the grays on monitor B also evokes a very
neutral impression to my visual system. But all hell breaks loose the moment
I turn both monitors on. The grays on monitor A decidedly appears green to
my visuual system relative to the grays on monitor B, which now appear
neutral to my visual system : impossible to convince my eyes that the grays
on monitor B are not neutral. Interesting.

This being said, I too believe that the white of the paper being compared to
the monitor calibrated white ought to be measure with a non-contact
instrument as Graeme suggested. In one experiment I recently made, I used
such a procedure, aiming the EyeOnePro at a blank *** of paper about six
inches away from the paper and used the measured chromaticities to calibrate
monitor A. The results: not a superior match between the paper and the
screen over using simple D50 chromaticities for calibration. Interesting.

Roger Breton



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