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Noob comprehending accurate exposure and a7s ii s-log2 recording

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Rhys Sherring
Noob comprehending accurate exposure and a7s ii s-log2 recording
on Sep 8, 2017 at 2:01:55 pm

I'm a Canon user and I'm shooting a short film with two a7s ii's next month. It's not a massively formal occasion, but I want to step up my game, so I've been doing a lot of homework to produce the best quality image I'm capable of. It's an entirely outdoor shot film, with a possible harsh contrasty Australian sun to deal with.

I have some questions from reading this article http://www.xdcam-user.com/2014/08/exposing-and-using-slog2-on-the-sony-a7s-...

Is there much difference between a7s and a7s ii slog2's? The article uses an a7s, where I'll be using an a7s ii.

When it says 'exposed at the Sony recommended "correct" 32% middle grey level', how do you tell its at that exposure level? Is it just a matter of pointing the camera at something that has grey and adjusting exposure so that grey appears at around 32 on the waveform (if i had an external monitor going)? That's a bit impractical for my purposes. What are some other ways? I've heard the histogram isn't the best to rely on when using s-log2?

His experiments explain that shooting 2+ stops over, but no more, of the Sony recommended base s-log2 level is beneficial for noise reduction etc. I'm just not practiced in such precise exposure setting. I'm only familiar with the simple histogram working with rec709 and stills photography.

Have people had much trouble shooting slog-2 with a7s ii's 8 bit, knowing 10 bit is much safer and better? Sounds like 8 bit is doable but just isn't as flexible. Surely it's still better than recording anything rec709 like? If there's no contrast in the shot at all, I should possibly just not use s-log 2 in such a case?

So it is recommended to load a custom LUT onto a live image external monitor of the s-log2 footage while shooting to see an accurate portrayal of the possible end game image since the camera's live-view of slog-2 will be so flat?

I plan to do an overhaul online self-education of grading in Resolve to work on all of the s-log2 footage. I will be the grader anyway. With the amount of tutorials and forums about, I think I can handle it.

Thanks, everyone!
Rhys.


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Chris Wright
Re: Noob comprehending accurate exposure and a7s ii s-log2 recording
on Sep 10, 2017 at 1:52:02 am
Last Edited By Chris Wright on Sep 10, 2017 at 1:55:51 am

just set zebra slog2 for 70 ire for skin either off talent or from 18% grey card, then back off a little. skin should fall between 50-80 ire with no noise as it slightly overexposes 2-3 stops to match how slog2 handles shadows. custom white balance each shot and set native iso to 1600 for most dynamic range. if possible, use ND's instead.

watch histogram for dynamic range and clipping if taking the whole scene into consideration.
if your exposing for highlights, set zebra for 109 with slog2. skin should not go below 50 ire or you'll get color noise.
for focusing, you can use gamma display assist-slog 2 to see in srgb.


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