DR: FS7 vs A7S

E

ectobuilder

Veteran
It is a known fact that the A7S has SLOG2, and the FS7 has SLOG3.

The A7S is however said to have 14 stops of dynamic range and the FS7 is also said to have 14 stops of dynamic range.

However if SLOG3 is 1.5 stops better than SLOG2, then should it stand to reason that the FS7 has at least 15.5 stops of DR?

The assumption here is their "said" stops of dr.
 
There's a huge difference between what the log encoding can store and what the camera can put into it. Slog2 is a bucket that can contain around 12/13 stops, Slog3 is a slightly bigger bucket (and a different shape). But the cameras can only 'pour' so much light into those buckets. In real world use that's about 12 stops, the A7s a little more. To all intents and purposes the FS7 seems to have pretty much the same sensor as the 700/5. The RAW output is identical at 12 bit, to me this means that you're looking at 12/13 stops.

So why do people claim 14 or 15 stops? It's because at the very ends of the curve they roll off giving the impression of extending range. So if you were looking at code values, say 8 bit for simplicity, the code value 254 was the 12th stop and 255 is the 13th stop, so technically there are 13 stops but actually there is one value between 12 and 13 which isn't very useful in the real world. Same for the shadows...

I hope that makes sense :)

cheers
Paul
 
It seems most people agree on the Canon C-series having 12 stops, but with Sony there is common dispute on the dynamic range. So at an advertised 14-15 stops, with a said 12-13 useful, how do the Sony's compare in dynamic range to the Canon's?
 
In my experience the Canon delivers enough DR in c-log mode. But c-log is not always a good idea.
It's still 8bit with a log-like profile which means the need for heavy grading/delogging in post.
Doesn't always look good. 8bit just isn't meant for this.
The Wide DR profile is much more useful for most situations.
Wide DR delivers approx. 10-11 usable stops of DR depending on your skills and the settings of Wide DR.

The Sony A7s can deliver up to 14 stops of DR with the slog2 profile. As a 8bit camera it suffers
again from the same problem. That said it's not always a good idea to use this profile (lowest ISO: 3200!!!).
I say usable range for most situations is up to 11-12 stops depending on your skills and the profile you use.

In the end it's more up to you than only up to the camera how many "useful" stops of DR you can squeeze
into your footage.

If you want the most DR you need to use at least 10bit log - better 12-14bit RAW footage. Much better handling
in post!
 
Dynamic range is one of those things for which you really can't compare numbers from different sources. In fact, I know that I can't even compare my own numbers from two different tests, ran with a similar methodology but with small changes because a year went by in between.

So, 12 stops? 14 stops? 15 stops? It doesn't mean anything.

What matters?

* Recording internally, the F3 with slog has 2-stops better DR than the C300 (half a stop in the highlights, plus a stop and a half in the shadows): here, 10:00 onwards
* The a7s has similar DR to the F3 (maybe a bit more, definitely not less): here (which-is-which here)
* My new a7s has 2.7 stops better usable DR than my old 5N: here (and my 5N is no bad performer at all; it is about a stop better than the 5D2, here)

I will be running a7s vs BlackMagic tests very soon. I'm trying to get a GH4 and a 5D3+RAW too, with no luck so far.
 
Samuel H said:
Dynamic range is one of those things for which you really can't compare numbers from different sources. In fact, I know that I can't even compare my own numbers from two different tests, ran with a similar methodology but with small changes because a year went by in between.

So, 12 stops? 14 stops? 15 stops? It doesn't mean anything.

What matters?

* Recording internally, the F3 with slog has 2-stops better DR than the C300 (half a stop in the highlights, plus a stop and a half in the shadows): here, 10:00 onwards
* The a7s has similar DR to the F3 (maybe a bit more, definitely not less): here (which-is-which here)
* My new a7s has 2.7 stops better usable DR than my old 5N: here (and my 5N is no bad performer at all; it is about a stop better than the 5D2, here)

I will be running a7s vs BlackMagic tests very soon. I'm trying to get a GH4 and a 5D3+RAW too, with no luck so far.
Click to expand...

This is true, because those last 2 stops are just splitting hairs that may or may not be there. 12 stops of actual range in the real world. What's also true is what does it matter, because 12 stops is plenty for 99% of cases

cheers
Paul
 
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