# Different calibration question



## glaufman (Nov 25, 2007)

Another thing I've been thinking about since reading the guide... the whole grayscale, then color points... i'm sure I've got things backwards, but please explain to me why...

It seems to me, since in all these systems grayscale (like all colors) is created by combining in the right proportions the 3 primary colors, wouldn't it make more sense ot adjust the primaries first, and then the grayscale (i.e. how the primaries get combined to create grayscale)? Aren't you just asking for trouble if you try to calibrate the sum (grayscale) before first calibrating the items you're summing (primaries)?

Yes, I know everything affects everything, and you have ot go back and check 1 after 2 and 2 after 1, but still, isn't calibrating the grayscale first sort of an exercise in semi-futility?


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## lcaillo (May 2, 2006)

You are assuming that the interaction in the same in both directions. Color management systems adjust the color of the primaries by adding or subtracting each of the other primaries. This has NO effect on the gray scale, but only on color decoding. The primaries, for gray scale purposes, are what they are. They are determined by the color of light produced by the phosphors, or by the filters in a filter based system like a DLP or LCD projection system. You adjust gray scale to get the white point that you want and tracking of that mix from dark to peak white. Think of this as the canvas upon which the color decoder works to create the right colors from the color difference signals (or color burst info in NTSC).


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## glaufman (Nov 25, 2007)

Thanks for the reply... with your help, I may have just reconciled this is my own mind... let me know if this makes sense...

I've been looking at it as when the picture wants something on the grayscale, the instruction says put out the 3 primaries in these proportions at this brightness... but what you're saying is that reality is closer to, when it wants something on the grayscale, it says illuminate these phosphors at these brightness in these proportions, and similarly, when it wants any color, including the primaries, it's still saying illuminate these phosphors in these proportions at this brightness, so the interaction from one ot the other should be subtle normally, and one could simply say you're treating white as if it was just another primary to be set to the right color, or conversely, you could call the primaries setting redscale, bluescale, etc...?


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