July 21, 2015 at 6:49AM

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Sony A7s S-Log: AVCHD better highlights than XAVC S??

Been doing a few tests with the Sony A7s' highlights. And Ive just found something that seems weird to me:

When filming the exact same scene, with the exact same exposure, if I record it in XAVC S, highlights clip at 100IRE. If I do it in AVCHD, highlights clip at 109IRE.

Again both are at the exact same settings (NTSC, S-Log, same ISO, etc.) except for the codec of course.

I open both in the latest PremierePro and use the Lumetri Scopes not clamped for both. Either in 8bit or float the result is the same.

Can it be that AVCHD is able to retain an extra stop of exposure???

Thanks a million

3 Comments

Sony might be doing this to stretch the exposure latitude for XAVC S, as you can conform 109 IRE back down to 100 IRE in post. ( so if you expose for 100 IRE the XAVC S will still retain detail up to 109 IRE )

July 21, 2015 at 9:51AM

1
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Guy McLoughlin
Video Producer
33682

The most likely reason is that Premiere recognizes the AVCHD file as legal range and stretches the data to fill the full range, but it likely doesn't recognize the range of the XAVC-S file and imports it as is.

I am not familiar with Premiere but you can use an application that allows to explicitly state the range of the video (for example, Resolve Lite) and repeat the test.

July 22, 2015 at 4:11AM

24
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Ezi Seel
659

Thank you very much for your answers.

The full info about this can be found in here, in case you are interested:
http://wolfcrow.com/blog/atomos-shogun-review/

Thanks

July 23, 2015 at 1:54AM

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