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Sony A7RV - Definitive Answer on Native ISO for Photo & Vid

rda

By rda,
in Sony Alpha Full Frame Cameras

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rda Apprentice

rda

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Trying to get some clarification on mixed messages on dual native ISO which seems to be different based on various factors.

Seems the camera native ISO is 100 & 320 (is this just for photography?)

For Slog3, I've gathered that it's 800 & 2500 (though some say it's a factor of 4 which would make it 3200)

What is it for HLG3?

Why is it different depending on profile?

Thanks for the clarification!

 

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Veres Deni Alex Collaborator

Veres Deni Alex

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I am not 100% sure about this, but from what I remember the reason why Base ISO differs from one gamma to another, is because each has different ways of exposing the image.

For example S-Log takes 2 exposures simultaneously and combines them together into a single frame to render you that high dynamic range, and I believe that is the reason why the minimum ISO is 800.

That's why Log gammas like Slog HLG will have rather higher base points that contrasty profiles like Still, Movie, Cine1 and so on.

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FunWithCameras Community Regular

FunWithCameras

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Different bodies have a different second gain point. All the Sony bodies start at 100, but the second gain may be at 320 (I believe that's the case for the A7RIV and A7RV - not surprising with the same sensor), but others have the second gain at a different ISO - you need to find a site which does testing (like photons to photos) to get the number. I think there is at least one sensor where the second gain is 800. All of that is for stills.

I don't shoot video, so I don't know much about it.

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rda Apprentice

rda

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I figured out that you have to multiply by a factor of 8 for SLOG3 and by a factor of 1.5 for HLG3... So for the Sony A7RV which has dual ISOs of 100 & 320, you get 125 & 400 for HLG3. I tested this in camera with the lens cap on and it seems to verify... grain increases until 400 where it drops down again. SLOG3 is 800 & 2500.

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