I am sure that CD and David from Datacolor will give you
an answer that is much more accurate and detailed than I; but I will attempt to
put forth some proposed answers to your questions.
1) The ambient light reading will depend on a number of
variables including the fact that over time the light source itself may change
both in color temperature and in intensity as the duration of its being turned
on increases and the source ages and/or warms up and/or external
light sources that contribute to the ambient light within a room may change in
intensity, direction, or type. Thus, the time between the measurements of the
different computers may contribute to different readings. A est for this
wqould be to take readings of the ambient light over an extended duration of a
single computer and see if the readings change over time.
2) The meaning and effect of a given reading like 128
across different monitors for even the same identical image will depend on and
vary with the chartacteristics and limitations of the individual monitors. Your
two desktop monitors may have similar properties and characteristics as well as
capabilities which may be very different from and greater or lesser than your
laptop monitor. The same may be the case with respect to the impact of the
video card on the monitors ability to render. You do not mention if the
desktops are using separate or the same video card and if that card is the same
as the one used by the laptop as well as the specifications of those video
cards and the ages of the three monitors. These factors all come into
play as variables. I think you really may have indirectly answered your
own question when you not that the desktop monitor displays have an Adobe RGB
1998 gamut whereas the laptop has a sRGB gamut; this indicates that the color
rendering capabilities of the two videocard/monitor combinations are not
identical and do not have the same identical color space in which values are
being interpreted.
At any rate, that is my two cents worth.
From: Jim Miller
Sent: Saturday, October 23, 2010 9:11 PM
Subject: [datacolor_group] Problem matching
monitors
I thought I had a handle on using the Spyder 3 but tonight I hit a
wall.
I have a desktop with two Dell 2408wfp monitors. I have them profiled at
6500 2.2 and 120cd.
I have a Dell notebook which I also profiled at 6500 2.2 120cd
with the same Spyder in the same room.
First problem is that the Spyder tells me the room is 89cd when run from
one computer and 120cd when run from the other. The location of the spyder
itself never changed.
I went ahead and profiled all three displays and then using Lightroom
displayed a white image.
The two desktop displays show the same color for white where the laptop
shows a different one. The desktop compared to the laptop appears greenish, the
laptop (not surprisingly) looks a bit magenta by comparison.
Questions:
Shouldn't the Spyder give a near identical reading of ambient regardless of
which computer is driving it?
Shouldn't 128, 128, 128 produce the same apparent image on all
three displays instead of obvious chromatic differences?
FWIW, the desktop displays have a gamut pretty close to AdobeRGB according
to S3Elite software 4.02.
The laptop is limited to approximately sRGB according to S3E
4.02
Win7/64
thanks
jim