AVS Forum Special Member
Join Date: May 2008
Location: San Francisco - East Bay area
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Yikers, so many "off" questions and replies...
A test pattern has no color temperature. The light produced by the TV or projector has a color temperature and for consumer video, that color temperature is 6500K but as explained in an earlier post in this thread, color temperature is a stupid and nearly worthless concept when you are trying to define accuracy in images because 6500K is very little affected by the amount of green or magenta in the image. In fact, there are shades of green and magenta that will measure 6500K with no problem. So STOP THINKING IN TERMS OF COLOR TEMPERATURE. D65 is the point in color space where all shades of white and gray should fall (for consumer video sources and displays). D65 represents a single point in the color space and at that single point, red, green, and blue will ALL be in proper balance, color temperature will be 6500K but remember, that's only going to tell you that red and blue are in proper balance and green is barely represented (leading to huge potential errors if you aren't focused on the D65 point).
Also... there is NO SUCH THING as IRE in Digital Video. Any manufacturer or software company who uses IRE is making a mistake. IRE is an analog video concept that defines the analog voltage level for white. There are no analog voltages in digital video, so using IRE now is just plain wrong and can be very misleading since consumer video's BLACK (0% white) is IRE 7.5 when you are working in analog video. If you are talking to someone who understands IRE and uses it correctly, you can end up confusing each other significantly because IRE and % white are NOT always interchangeable. In digital video we should only ever use % white or digital levels (like 16-235).
Lastly, there's no such thing as D6500K... you have D65 or 6500K but not both together -- well, that's not quite right. The color temperature of the D65 point is indeed 6500K, but there are many coordinates that will measure 6500K for color temperature, but only ONE of them is the D65 point where red, green, and blue are all in proper balance for white and shades of gray. And D6500 doesn't exist, if you see that, the person typing it just doesn't know enough about the topic yet.
"Movies is magic..." Van Dyke Parks
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