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by adrian_b
46 days ago
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That is why I said "standard gamma curves", and not "standard gamma curve", as each standard specifies a slightly different curve, for various reasons. Such differences in standards already existed in analog television, because, depending on how they were made, the CRTs also had slightly different transfer curves from grid voltage (where the video signal was applied) to anode current (which is proportional with the luminance of the pixel component), and the regional TV standards accounted for the dominant manufacturers of the CRTs sold in that region. |
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NTSC was gamma 2.2, and PAL/SECAM was gamma 2.8, which was indeed initially partly caused by local manufacturing differences before international brands took over, but neither "standard" was really followed by anyone. In the end, concluding that it was all a total mess, we split the difference in the early 90's by formally defining both to gamma 2.4 in BT.709. As such, their curves are the same.
(Manufacturing derivation was outside the scope, as manufacturers did whatever was convenient or sold sets, going all over the place with their response curves regardless of what region they were from or targeted. This remains true today - see any new TVs standard color response.)