Datacolor User to User Support Group.

In a message dated 5/7/07 3:13:00 AM, eeshdewan@... writes:


> When we have calibrated our display to gamma 2.2, 6500K, white luminance 
> 90cd/m2 and black luminance to 0.3cd/m2 and then open the colorimeter window to 
> measure the color temperature of white, the reading show 5500 odd Kelvin and 
> not 6500k. Is there something that I am doing wrong?
> 

It sounds like the colorimeter window is not measuring your calibrated 
whitepoint, but your native whitepoint. Calibrate your monitor, go to the Before and 
After screen at the end of the software, open the colorimeter window, and 
check the K value in both before, and in after, mode. 

Keep in mind that Kelvin   values are highly leveraged, and that a variation 
of hundreds of K points can be as little as .003 difference in measured xyY 
values. This means that end user spectros and colorimeters (and to a suprising 
degree, even laboratory devices) are not capable of working down to the 100k 
level, as large a number as that sounds. Frankly, K measurements should be 
reported to the nearest 500K, not the nearest 1K, to reflect the actual value of 
the measurements. 6 and a half thousand K as the next unit from 6 thousand would 
be more reasonable units of measurement. Adding all those extra units makes 
end users assume that the tolerances are actually that close.

C. David Tobie
Product Technology Manager
ColorVision Business Unit
Datacolor Inc.
CDTobie@...
www.colorvision.com


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