One for Alan, Sony Hypergamma - DVdoctor.community

SimonMW Senior Member Join Date: Nov 2004 Location: UK Posts: 1,172

Default One for Alan, Sony Hypergamma

I´ve just been reading a new document on the Sony website about how to use their Hypergamma modes on cameras like the F900, PDW-700, F350 etc.

Confusingly (for me) they have stated that Hypergammas 1-2 should be used if you want to output without modification to systems that have a 100% white clip, and to use Hypergammas 3-4 if you are grading.

Now, I can understand why they are saying this, because Hypergammas 3-4 go right up to 109ire. However I am still confused.

Hypergammas 1-2 not only stay within 100ire, but they peak well below it! This creates a very flat looking picture that I would not consider using without some form of grading.

1-2 appear to compress more contrast range into the signal, even though 3-4 are using more tonal range. Though I could be wrong (and often am).

Alan, have you tested all four Hypergammas? And if so, what did you find that the best uses for them would be?

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http://www.simonwyndham.co.uk

SimonMW

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Alan Roberts Moderate Moderator Join Date: May 1999 Location: Mugswell, Surrey, UK Posts: 11,040

Yes, all tested. And the instructions are correct, 1 and 2 are two different curves, both go not quite up to 100% video level but cover the full exposure range (about 600% depending on the camera), they deal with the mid-tones differently from each other, and prouce skin tones at lower video levels than would the normal 709 curve with or without knee. Therefore, they compress contrast quite a bit. 3 and 4 curves are each identical to 1 and 2, except that they are stretched vertically to fit into 109% of video range in stead of just under 100%, still with the same exposure range. Therefore they produced skin tones abit brighter.

So, curves 1 and 3 are identical except that 1 peaks near 100%, 3 is stretched to peak at 109%. 2 and 4 are also identical, with the same peak levels as 1 and 2.

There´s a very good reason why 1 and 2 don´t go exactly to 100%, there´s a small guard space left available for the overshooting that excessive detail enhancement produces. That´s absolutely normal. 3 and 4 both go right up to 109%, because they assume you know what you´re doing and will set other parameters to make sense. That´s one reason why I still define normal curves and knees, to give you the options.

You´ll find all this covered in the BBC settings docs for the cameras.

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Alan Roberts, happily retired from Auntie Beeb

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