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Old November 19th, 2003, 01:34 PM   #1
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why "Y" (and not "L") for luminance?

Does anyone know why the luminance component is marked "Y" instead of "L"?
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Old November 19th, 2003, 04:15 PM   #2
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Many decades ago the C.I.E. defined a trichromatic color concept (color space), underlaying all color TV systems. They proposed a 3-dimensional space (X,Y,Z) which was transformed in such a way that only the Y axis represented the "luminance" of any color belonging to that space. The "Y" in color TV is being derived from this representation but is being gamma pre-corrected so that its numerical value(IRE) is no longer equal to the "luminance" seen on a TV screen.
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Old November 24th, 2003, 08:51 AM   #3
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Interesting... I didn't know that. Thanks!
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Old November 24th, 2003, 08:36 PM   #4
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Andre,

do you know why, on SONY gear,

that

Y is Green or Luminance
R-Y is Red or Chroma
B-Y is Blue

just curious
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Old November 25th, 2003, 04:39 AM   #5
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Allmost all manufacturers apply configurable connections for analog signal in/output. There is no "technical" reason for specific allocations. Only minimizing the number of connectors and output/input amplifiers (and cost!) is the point. In general if cinch connectors are involved they can be set for RGB or Y, R-Y, B-Y or composite, or (if not taken by a Y/C hosiden connector)also as Y/C. Also SCART connectors often have configurable pins. The Y signal (in Y/C or Y, R-Y,B-Y setting) and the green channel (in RGB) and the composite signal are mostly taken on the same connector. Chroma (in Y/C connections) and red (in RGB) and R-Y (in Y, R-Y, B-Y setting ) are also assigned to the same connector. Blue (in RGB) and B-Y also shear the same connector
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Old November 25th, 2003, 06:57 AM   #6
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I could be mistaken, but I think John is asking why Sony uses the Y/R-Y/B-Y designations, as opposed to the more often seen Y/Pr/Pb designations. Are they the same thing? Is this just a bunch of propietary naming nonsense (which Sony seems to be fond of)?

Also, Andre, respectfully, would you mind elaborating on your two previous points with slightly less technical language. There's a lot of stuff in there that flies over the head of those of us with no engineering background.

Thanks.
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Old November 25th, 2003, 10:33 AM   #7
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Sony's designation is actually easier to understand.

Y=Luminance
R-Y=Red - Luminance
B-Y=Blue - Luminance

Makes it easier for the average consumer.
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Old November 25th, 2003, 03:24 PM   #8
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Stu, it's a bit a long story..., could you tell me what exactly you wanted to know?
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