slog2 = 8-bits in 14 stops?

[toke lahti]

Sorry if this is already discussed here, but I couldn't find anything.

I'm just wondering when comparing to "normal" video DR, does slog2 help so much, that even if you have only half the bits per stop, you don't need them?
I know that log scale puts more of the few bits where they are most needed, but still, isn't there less bits per stop than used to be?

(Edit: of course I'm asking this because I'm thinking of buying a7s...)

 

[Samuel H]

It's far from 14 stops. In fact, it's just 1 stop more than Cine4 (and macgregor will dispute that, he measured them to be just as wide).

This is the curve I got:

Each wedge is a third of a stops, and there's still some signal in the bottom, so that's about 12 stops (the difference with other cameras is that nearly all of the available DR is usable), with 24 RGB values per stop in the mids and highs (much less in the shadows, as usual).

10 bits would be better, and in theory 8 bits could easily be not enough for this, but in practice it works great. I have a personal variant of slog2 called Flaat (slog2 with cinema color and some color tweaks), and that's what I use 99% of the time. YMMV

 

[Erwan]

Hi Samuel, could you please share your "Fllat" profile ? is it still as s-log2 native iso 3200? thx.

 

[Samuel H]

Flaat for the a7s

I would call it "native ISO 1600" because I set it to 3200 in the camera but always overexpose by one stop (I set 1600 in my light meter).

 

[Neutral]

Flaat for the a7s

I would call it "native ISO 1600" because I set it to 3200 in the camera but always overexpose by one stop (I set 1600 in my light meter).

i've read about that flaat PP the other day I think i might try it out. I haven't been shooting long but I always hear people talking about over exposing by 1 stop with sony camera's. Can you explain what that means? i understand what over exposing is, but what does 'by one stop' mean? And what is the benefit of doing this?

 

[Samuel H]

If I set my camera to ISO 3200 and my light meter to ISO 1600 and follow what my light meter tells me, I'm overexposing by one stop.

Same if I set my exposure as the camera tells me to (where the exp meter is at "0") and then open aperture by one stop.

Doing this means I get less noise, more headroom in the shadows, but less headroom in the highlights. The a7s can cope fine with up to 2 stops of overexposure, but 3 is often too much, resulting in ugly skin. I only go for 1 stop since that's enough to reduce noise and I don't want to lose a lot of headroom in the highlights.

 

[ReelWorksMedia]

What's your best practice for proper exposure using only camera tools without a meter. Just curious about your workflow for the as7s. Thanks.

 

[Samuel H]

Me? Beware that I'm not even a pro, much less any sort of guru. But if you're curious...

a) If I have time to prepare the shot, and no problem carrying lots of gear: light meter
b) If I have time to prepare the shot, but I'm not carrying the light meter: use the stop meter from the camera and a grey card. It's very well aligned with the reflective readings from my light meter.
c) If I don't have time, I won't be carrying the light meter, so: either use b) at some point and keep that unchanged, or just eyeball and fix in post if needed.

BTW I'm building a set of LUTs to adjust exposure in a7s slog2 footage in an accurate manner. Like "bring it up a third of a stop", etc. I'll release those soon.