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Old 16th February 2023, 12:12   #79  |  Link
FranceBB
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Location: Royal Borough of Kensington & Chelsea, UK
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Quote:
Originally Posted by DTL View Post
1. About several decades already may be from beginning of rec.601 digital the good quality broadcast-class video cameras had HDR internal processing - it required to have about 600% non-clipped dynamic range above nominal white (for 2/3 chips classic SD camera). Better product may have 1000% and more range above nominal white. At the 'before public HDR standards' time the camera control person may either hit AUTO KNEE option or manually play with KNEE POINT/ KNEE SLOPE adjustments per scene to have _non_standardized_ HDR compression of scene highlights into SDR valid codevalues range (8 or 10bits)
That is correct if it wasn't for the fact that cameras originally only had around 6 stops which leaves no headroom for highlights. Only after that, they improved beyond the 6 stops and nowadays they're doing what you described internally. But in SD days? No chance.
But even nowadays, some cameras don't really have many stops and therefore they don't have a large enough bracket to get all the frequencies.
This is just an example: look at the sunlight, the camera sensor had too little stops to be able to record the sky and therefore it's clipped out at 0.7V.



This is a classic example and it's something my colleagues and I refer to with "the sheet is too short". With that expression, we mean that the camera has a bracket of x stops and no matter if you move it up or down, you'll always end up sacrificing something, be it the whites or the blacks of the image. In 99.9% of the cases, the person talking (i.e the presenter) is the most important subject, so that one is where the stops focus around and you'll be able to clearly see the face of the person talking, however the sky will be clipped out (in fact it's white). If you did the other way round, you would have preserved the sky, but the face of the presenter would have been completely averaged out in the dark region and you wouldn't be able to see it.

This, again, is all occurring in BT709 SDR 100 nits and it just shows the limits of SDR.
Sure, you could have a feed recorded by HDR cameras in a totally logarithmic curve like Slog3, Clog3, LogC etc and then perform the BT709 mapping, but realistically, for news, this ain't gonna happen.
One day, though, when everything will be HDR, the cameras will be able to record automatically in let's say HLG and then the same feed could be used live without additional mapping or conversions unlike Slog3, Clog3, LogC etc that would require mapping to PQ and you can bet anything that if today this technology was already widespread and implemented and everything was shot and recorded and aired in BT2020 HLG 1000 nits, the sky would have been there and it would have been blue

Last edited by FranceBB; 16th February 2023 at 12:16.
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