Originally Posted by LarryInRI
I agree that there is no perceptible difference or should there be any but 6500K is not "shorthand" for 6504K. There is a true physical reason for the difference and it has to do with a more precise determination of Planck's constant. If you want to discuss the physics of the situation, I will be glad to do so in PMs. Some of us are not dummies, you know.
6500K and the xy coordinates where it crossed the Planckian locus of a black-body initially was defined by a committee as D65. Subsequently, a more precise value of Planck's constant was determined and the locus shifted because of this. The committee kept the xy coordinates of where the initial color temperature crossed the locus the same. But this meant that the color temperature was actually 6504K for D65. It's that simple.
Whatever. 6504 doesn't matter a WHIT when discussing calibration or color temp unless you are a color scientist working in a lab. It doesn't matter AT ALL why 6504 is the right number. It is the right number and everybody who knows ANYTHING about calibration understands 6504 is the right number, but we all still talk about 6500 BECAUSE the "4" is so far below the threshold of human visual perception compared to "0" that it DOESN'T MATTER if we say 6500 or 6504 when talking about home theater. If I was in a lab working somewhere that it MATTERED whether you were talking about 6500 or 6504, I'd use 6504. If I'm talking to someone about home theater, 6500 is close enough. And I thought I
- I've never seen a video display that could EVER produce a 6504 measurement result two times in a row, even if the measurements are made seconds apart. Even when measuring with a $55,000 labratory grade spectroradiometer in a temperature and lighting controlled lab environment with stabilized and "perfect" power so the power line can't influence the TV/monitor in any way.AND ON TOP OF THAT
- meters used for home theater calibration, even expensive ones in the range of $7000-$25,000 can't produce a 6504 reading two times in a row from a calibrated (non-video) source that is constantly 6504. And the variation you get will be several times the difference between 6504 and 6500.AND THAT MEANS
- the difference between 6504 and 6500 is considerably smaller than the (short- and long-term) tolerances of video displays (including projectors) and meters typically used for home theater calibration.Bottom line...
in the real (home theater) world, the difference between 6500 and 6504 is MEANINGLESS. If you are a color scientist working in a lab where it matters, use 6504. If you are a home theater enthusiast... meh... use what's easier to remember. When we calibrate we (should) focus on how to get each grayscale step closer to d65. Color Temp is meaningless to a calibrator who is focused on the right thing (d65).
I guess I am still pretty anal.