Quote:
Originally Posted by 2Bdecided
TV levels: 16=black, 235=white
PC levels: 0=black, 255=white
The PC levels are kind of obvious, so the question becomes: why were the TV levels defined with headroom below black and above white?
This dates back to 1982 in ITU Rec 601. It's simply that, in a studio environment, levels can't be quite as carefully controlled as in a PC, and processing like sharpening and band limiting create overshoots. If you clip these overshoots, you can create even more overshoots further down the line - so to allow for not-quite-right levels, and overshoots that don't spread out in a hideous way, a little headroom was left at either end of the scale.
These are the standard levels for YUV video. Everyone knows what they are. Changing them would only create confusion, without any benefit.
Cheers,
David. |
I guess another question then is why don't PCs use video levels? It would have saved a lot of problems, especially as more and more people are now plugging their PCs into their TVs.