While making routine (!) measurements on a display, I
measured an LCD display luminance (Samsung 950B) by
placing an Eye-One Pro spectrophotometer in the usual
position, which is vertical, i.e. at noon, then made a
second measurement with the instrument placed at
nine-o-clock.
The vertical measurement gave me 117 cd/m2 while the
second one gave me 106 cd/m2. The CIEDE2000 color
difference is about 2.4.
BTW, the values are the same for noon and six-o-clock, and
the same for nine and three-o-clock.
I immediately suspected a polarization effect since LCDs
are based on this effect. I looked at the display with a
polarizer and saw that I could go from extinction at 45
degrees to max transmission at minus 45 degrees.
I also checked that by installing the Eye-One ambient
diffuser and making the two measurements, the measured
luminance were equal (although much smaller), which was
expected since the diffuser de-polarizes the light.
While having polarized light out of an LCD is not a
problem, its effect, when combined to a measuring
instrument, is bound to raise questions to anyone checking
their display accuracy.
For example, many will open a color chart image on their
screen; they will then measure some samples with the
instrument placed vertically, and other samples, the ones
located in the screen lower part, with the instrument
placed horizontally.
I suspect the Eye-One Display is less sensitive to this
effect.
Does anybody else see this?
Please include your instrument model in your answer.
Thank-you,
Danny Pascale
email@hidden
www.BabelColor.com
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