A7s sample footage

cpc said:
You mean 10-bit luma, 8-bit chroma. :)
It will actually be 4:4:4 10-bit luma, 9-bit chroma with 8-bit 4:2:2 hdmi output downscaled. And yes, should be better. How much better remains to be seen.
Click to expand...


Sorry about the mixup, that is what I meant. I am profoundly dyslexic as is probably obvious from my posts. Thank God for finding a visual medium to play with.
 
paulcurtis said:
I'm not sure everyone is really getting Slog2 here, it's not about dynamic range it's about the distribution of light values in a quantifiable way. Slog2 offers a better way to record and to manipulate the image afterwards.

The cinecurves may contain the same lowest black value and the same highlight pixel of white but the distribution of values between differs wildly, most cine curves will very quickly roll off the very top highlights so perhaps the top 2 or 3 stops might be described in a handful of actual code values, it looks like clipping basically and it practically is.

Remember we have a paltry 256 steps to describe this scene. a 12 stop scene in RAW minimum needs 4096 steps but really needs a 16 bit container, 65k steps. So you can see that an 8 bit output is a massive difference.

Light is a doubling of value, so for 12 stops that very last stop occupies code values from 2048 to 4096, a massive waste. Log is an attempt to distribute stops so that each stop takes a similar number of values. In our 8 bit case describing each stop with 20 values would be possible, Slog2 sort of does this but changes the curve in the shadows to make the best of it. The black is also elevated so black is not 0.

When we talk about stops over and under it's difficult to quantify with cinecurves because they are not officially defined - there's no mapping between real world stops and what's in the file.

The point of Slog2 is that it is a mathematically defined curve that an NLE or Grading app can unfold back into scene linear space, so that the light is photometrically accurate. If you reduce exposure via footage that has been correctly interpreted as Slog2 then your scene will look 'right'. Much like RAW. RAW is also a known photometrically accurate way of storing light, although it doesn't use a log curve (usually), it's simple linear by nature.

Each Slog container sony has done has tweaked the curve a little. The original Slog was created for the F35 i believe and was designed to hold the range of that camera. Slog2 was more for the F5/F55 generation and has a range of 13.5 to 14 stops. Slog3 is a tweak of this that opens up the shadows and makes the actual log part of the curve more like LogC which is the basis of AlexaLogC and is a slightly better, truer log curve.

The thing with range is that it's difficult to quantify. You can peg mid grey at whatever you want and then you can tell very easily where clipping is because, well, it's clipped. However where do you place black? Because the darker you get the noiser and it's up to you to decide when has the noise taken over the signal. I think the FS700 has maybe 4 stops under grey on a practical level based around the 12 bit output.

It would be useful for Sony to issue a white paper explaining how they arrived at a base iso of 3200. Like cpc said i feel there is some definite messing around happening between the sensor and output - much the like FS700 which requires an exposure gain for the RAW footage to work correctly. It's not wrong, but it would be useful in understanding how the sensor works best.

cheers
Paul
Click to expand...

Great post, thanks!. This explains a lot. When I first starting testing C-log, I reported that there was no improvement in DR over Canon's WideDR gamma, and many didn't believe me. I have not had the time to do any serious testing of S-log, but now I won't bother. And I have noticed that the black level setting while using S-log gamma is disabled (or at least has no effect), and black is definitely above zero, about a stop from what I can tell. From a few quick tests that I have done with the A7s, the S-log curve is really flat, and it does retain far more highlight data (even better than Canon's), but you better nail your exposure if you want it to hold up in post. And if it's a flat scene you're shooting, it's actually working against you. The fact is, a lot of what we shoot doesn't need more than 11 stops of DR spread out over a good, traditional gamma curve such as cine1.

I first reported that I was impressed with the DR using the Rec709-800% curve. The manual states that the Rec709-800% curve is to be used as essentially a LUT for the Slog gamma (a visual tool for analyzing Slog on the LCD). Since I read this I've done some testing with the cine1 curve and I find it to yield the same DR with a more useable profile (and this too holds up VERY well next to a C100 image). I'm guessing that within a week or so people will start putting up custom profiles with samples.
 
strancali said:
Kholi, you got it man. It should arrive on Saturday. I'll let you know and you test the s*%t out of it next week. I also have the metabones v4 adapter so throw that 70-200mm of yours on it :)
Click to expand...

Godlike. I was gonna ask about the adapter.

Does anyone know of Odyssey can take 4K HDMI yet? I can grab one of those for the week as well if so.
 
Here's a frame from the rolling shutter test I sent to Samuel H. This would be a mess of aliasing and moire - especially the rooftop - with just about every other DSLR/EVIL cam except the 5d3, but that wouldn't be as sharp unless shooting raw.

Sequence 01.Still002.jpg
 
L1N3ARX said:
Dammit! lol, well after I test it out, I'll just return it for the new version. I swear III was the latest version when I ordered, ah well. Can't wait to get some shots with the 70-200mkII & 85 1.2 tomorrow.
Click to expand...

Hey Roman, yea get the latest as it stops the internal flares better.
 
Every time I see a7s footage I think of the Sixth Sense "I see yellow people".
But serious im sure I will find a solution for that. In camera tweaking or FCPX LUT.
I had this with my FS100 on magenta skin tones, and when I understood the camera I got it away.
 
I've seen some pretty neutral SOTC footage from other users. I think the problems are with SLOG2 and are exposure/ND related. Cine 1 mode looks like what I'll be using 90% of the time. Clean, beautiful and the DR looks plenty good to me.

Download this sample from PhotographyBlog.com.

http://img.photographyblog.com/reviews/sony_a7s/sample_images/sony_a7s_02.mp4

There are a couple others in 60p and 120p of the same scene as well. Nice clean capture though maybe a tad overexposed for the highlights by a tiny bit. I think it's a fantastic image overall to work with. Main link: http://www.photographyblog.com/reviews/sony_a7s_review/sample_images/
 
Last edited:
I think I told Roman the o'er day that PP4 or 5 looks like what I'd go for instead of SLOG. ARe either of those Cine 1?
 
Kholi said:
I think I told Roman the o'er day that PP4 or 5 looks like what I'd go for instead of SLOG. ARe either of those Cine 1?
Click to expand...

From User Guide:

Using the preset of the picture profile The default settings [PP1] through [PP7] for movies have been set in advance in the camera based on various shooting conditions. MENU → (Camera Settings) → [Picture Profile] → desired setting.


PP1: Example setting using
 
You must log in or register to reply here.
Back
Top