The illustration in the link you give shows that the top
polariser is at 45 degrees, which corresponds to my
observation.
What I did not mention in my first post is that I also
measured the luminance with the spectro aligned on the
plus 45 and -45 degrees, relative to zero degrees at noon,
which correspond to the maximum extinction and max
transmission I saw when looking at the display through a
polariser (Polaroid sunglasses would do the trick).
However, I did not measure a larger difference than
between noon (vertical) and three-o-clock (horizontal)
positions. This only means that the optical components
which are sensitive to polarisation inside the spectro are
not necessarily aligned with the outside shape of the
instrument.
In the CRT era, still there for many, this was not an
issue. The LCDs are different beasts. If we position the
(spectro) instruments as shown in all calibration
procedures (vertical for GMB instruments), then the
results should be consistent.
But, as soon as you make a spot check, holding the
instrument by hand, then there is a significant chance
that you will tilt it and "artificially" induce an error.
At least a warning should be given at this effect.
Danny Pascale
email@hidden
www.BabelColor.com
On Mon, 26 Feb 2007 11:58:33 -0300
Lorenzo Ridolfi <email@hidden> wrote:
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.
