why "Y" (and not "L") for luminance? at DVinfo.net

Stu Minnis · November 19th, 2003, 01:34 PM

Does anyone know why the luminance component is marked "Y" instead of "L"?

Andre De Clercq · November 19th, 2003, 04:15 PM

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.

Rob Lohman · November 24th, 2003, 08:51 AM

Interesting... I didn't know that. Thanks!

John Jay · November 24th, 2003, 08:36 PM

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

Andre De Clercq · November 25th, 2003, 04:39 AM

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

Stu Minnis · November 25th, 2003, 06:57 AM

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.

Tony Singh · November 25th, 2003, 10:33 AM

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.

Andre De Clercq · November 25th, 2003, 03:24 PM

Stu, it's a bit a long story..., could you tell me what exactly you wanted to know?

November 19th, 2003, 01:34 PM	#1
Stu Minnis Regular Crew Join Date: May 2003 Location: Virginia Beach, VA Posts: 44	why "Y" (and not "L") for luminance? Does anyone know why the luminance component is marked "Y" instead of "L"?

November 24th, 2003, 08:51 AM	#3
Rob Lohman RED Code Chef Join Date: Oct 2001 Location: Holland Posts: 12,514	Interesting... I didn't know that. Thanks! __________________ Rob Lohman, visuar@iname.com DV Info Wrangler & RED Code Chef Join the DV Challenge \| Lady X Search DVinfo.net for quick answers \| Buy from the best: DVinfo.net sponsors

November 24th, 2003, 08:36 PM	#4
John Jay Major Player Join Date: Sep 2002 Location: US & THEM Posts: 827	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 __________________ John Jay Beware *PLUGGER-BYTES*

November 19th, 2003, 04:15 PM	#2
Andre De Clercq Major Player Join Date: Sep 2002 Location: Belgium Posts: 804	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.

November 25th, 2003, 04:39 AM	#5
Andre De Clercq Major Player Join Date: Sep 2002 Location: Belgium Posts: 804	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

November 25th, 2003, 06:57 AM	#6
Stu Minnis Regular Crew Join Date: May 2003 Location: Virginia Beach, VA Posts: 44	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.

November 25th, 2003, 10:33 AM	#7
Tony Singh New Boot Join Date: Sep 2003 Location: Toronto, Canada Posts: 14	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.

November 25th, 2003, 03:24 PM	#8
Andre De Clercq Major Player Join Date: Sep 2002 Location: Belgium Posts: 804	Stu, it's a bit a long story..., could you tell me what exactly you wanted to know?