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Re: HDR question

Re: HDR question

James Barber

If you haven't drastically over or underexposed anything, the FS7 in S-Log and the 10-bit codecs definitely give you enough dynamic range to grade in HDR, but not huge grading latitude. Think of grading 8-bit footage for 8-bit playout: it works, but it doesn't let one grade aggressively. 12-bit or higher codecs are best for HDR grading, as it's a 10-bit out. But definitely doable, especially as HDR should mostly just be regular light levels from IRE 0-100, and bright brights from 100-1000+.

Big things for HDR grading in terms of exposure is as little clipping as possible so there can be detail in those highlights, and as much bit depth as possible for colour information in those extreme gradients.

Not many cameras record to any form of HDR natively. The ones that do will record in HLG (Hybrid Log Gamma) and Rec2020 colour space. But crucially, they don't actually record more data than log at the same bitrate – it's just a different gamma curve. Very few cameras record a big enough gamut to actually make good use of the Rec2020 colour space yet (F65 for instance).

That said, HLG is a sort of 'broadcast' standard for HDR that is being pushed for live TV, so NHK might want stuff shot in HLG (Hybrid Log Gamma) to reduce post time. Same how some places currently prefer Rec709 footage rather than Log.

I would say something like "the dynamic range of the recorded footage is HDR compatible when graded, but has been shot in Log format to preserve the maximum range of light and shadow".

Hope that 2cents helps.

James I. Barber

On 15 March 2018 at 12:21, jmselva <jmselva@...> wrote:
Hi all.

I have shot a doc on a FS7 in XAVC-I / Slog.
It is now being sold to NHK Japan and they are asking if it was shot in
Now, being that all modern cameras are HDR capable with they 13+ stops
and that it is merely a post decision to do or not a HDR version, I find
the question odd.

But I do have a question though : does the XAVC-I codec and Slog limit
in any way the possibility to do a HDR version after the fact ?

Thanks in advance.
Jean Marc Selva, DOP, Paris.

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