My own Sony A7s test - 4K resolution, dynamic range, noise and GH4 comparison

macgregor

macgregor

Veteran
Alright, so here we go. I'll be super quick. Lots of tests, most of the results are self-explanatory. Tests done in Madrid in early August with my friend Enrique Pacheco and the help of Adrián Cabello.


Dynamic range

Tests performed in studio, under Kinoflo lights. Zeiss lenses. Footage recorded internally as 1080p XAVC-s and externally via Blackmagic Ultrastudio4K as ProresHQ. Evaluation/processing done in Davinci resolve.

a7sstuder.jpg



Sony A7s
cine4 200ISO: 12 stops. 11 usable. +4 -6
S-Log2 3200ISO: 12 stops. 11 usable. +5 2/3 -4 1/3
PPoff 100ISO: 11 1/3 stops. 9 usable. +3 1/3 -4 2/3

Panasonic GH4
CineD 200ISO: 11 1/3 stops. 10 ⅓ stops usable. +3 2/3 -5 2/3






And for comparison porpuses:
old good Sony F35 S-Log 450ISO: 14 ⅓ stops. 12 ⅓ stops usable. +7 -6 ⅓ (+6 ⅓ -5)



Comments:
On usable DR I'm throwing away the last stop, which is at least 50% noise and barely gives any extra info while being extremely noisy. This is of course a personal decision.
A7s does not live up to the hype. I don't know where those 14 stops figures come from. Certainly we didn't see anything near that.
Biggest issue with S-Log2 on the A7s is that while achieves good results on highlight detail, is a bit short in shadow detail, and what's worst, below mid gray it shows way more noise than any of the other modes/cameras.


And how do cine profiles affect DR on the A7s?
I didn't bother testing every single picture profile on the camera otherwise I would never have finished. But here's a quick comparison:

 
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ISO vs noise



Remember to watch these files at 4K (for those who can).




To my eyes, the GH4 in CineD 1600ISO produces similar noise levels than the A7s at Cine4 12800ISO. So lets see them side by side:

 
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Alright lets take this new toy outside and see what's capable of!

Some 4K footage:


Now lets compare 4K downsampled to 1080p vs recording internally at 1080p.

Unless you're dealing with extremely high detail scenes the difference is not huge. It's there but if you're filming people, interviews or products I think it's fine.
Of course, by recording 4K we'll get a pretty nice 1080p at 444 sampling.



Lets see now how does the A7s in S-Log2 mode at 1080p compare with the 5 year old state of the art Sony F35, which uses a +5K CCD sensor to render a 1080p signal:
Hey, the A7s holds up pretty well. A bit less DR. It's softer and maybe colors are a bit more digital. But for a $2500 mirrorless camera, it's not too bad. Also I didn't encounter any issues from the fact that the A7s shoots only in 8bit. (yes you just read that, so stop the nonsense about 8bit cameras being crap. Sure I'll take 10bit over 8bit, but 8bit is still good 99% of the times. HDcam and DVCproHD were both 8bit goddammit!).
Then of course the A7s strugles with massive rolling shutter issues and those ugly highlight edge artifacts...

highlight%20edge.jpg
 
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Resolution

We set up both cameras one of the top of the other and chose a rooftop view that would give us lots of information of each of the camera's performance: resolved detail, real life dynamic range, possible aliasing...
Sony A7s was set to: cine4, pro, detail -5, Using a zeiss 25mm at f8 - 1/250 200ISO.
Panasonic GH4 was set with the same ISO, shutter and aperture. Cinelike D, -4, -4 -5 -1, and Panasonic 7-14mm lens set at 9,9mm.
Having so many picture profiles and settings, the variables in each camera are endless. But we found these settings to be the best or at least the most representative of each camera.


4K JPG files (right click to download):

01.A7s%20UHD.jpg


02.GH4%20UHD.jpg





Micro-contrast differences are obvious. However I don't see major differences in resolved detail.
Here are some crops:

resolucion.jpg



Aliasing issues? Yep, both cameras seem to show color aliasing. In this example only the Gh4 shows some problems but I've seen similar effects on the A7s as well.

aliasing%20color.jpg




Another crop, where we can see real life dynaic range differences:

detalle%20en%20cielo.jpg
 
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Great tests! Thanks for sharing- It seems like 14 stops on an 8bit camera seems like a bit of overhype in terms of usable DR (from my semi-novice observations). However, I'm curious if ETTR would give you a bit more using 8-bit as heavily discussed on the forums here. Also, turning down the detail to -7 seems to be a fairly common response to ugly highlight artifacts.

Did you account/disregard these two things or was this testing pre-discovery of these little camera specific workarounds?

P.S. its amazing how close you got the grade to match between the Gh4/A7S

On the GH4, was CineD at default contrast settings? Sorry if I missed that, looked twice, couldn't see where you mentioned it.
 
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I also decided to give a try in stills mode. There's been so much hype about the fantastic dynamic range and sensitivity of the camera that I was of course dying to test it.
So I just took it around for some tests along the Nikon D800.

I gave both camers a hard time, trying to push the limits with high contrast scenes:

a7sd800p1.jpg

Original scene. Shot in raw. Exposed for the higlights. Same exposure in both. 100ISO.

Now lets see what comes from them once we open them in Photosop using camera raw:

a7sd800p2.jpg

A7s on the left. D800 on the right. Same camera raw settings (pretty much shadows boosted all the way up, and highlights all the way down).

And a closer look:
Untitled-1.jpg

Glups. The A7s shows some really nasty noise, less shadow detail, more electronic colors, and ugly aliasing on her hair. Sure, the D800 benefits from downsampling a much bigger image. But the A7s was supposed to be super clean and offer up to 14 stops of DR. Not good.


Second attempt:
a7svsd800p3.jpg

Original scene. Shot in raw. Same exposure in both cameras. 100ISO.

c01.jpg

c02.jpg


A7s on top. D800 on the bottom. Right click to save full size. No comments.

I would expect the A7s too destroy the D800 on higher ISOs, but for the kind of photography I do, I usually like to keep the camera on its native ISO as much as possible.
 
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Macgregor did you take any stills with iso bumped up on either camera? I am going to guess the a7s will be less noisey the higher the iso, I mean that is what I found.
 
Dafilman21 said:
Macgregor did you take any stills with iso bumped up on either camera? I am going to guess the a7s will be less noisey the higher the iso, I mean that is what I found.
Click to expand...

I'm pretty sure you're right. But I don't need to shoot at 12000ISO anyway.
 
Makes sense the a7s is sorta kind of a specialists camera, it allows for you to shoot in a different way than a lot of other cameras out there. Thanks a lot for taking all that time to test these things out!
 
macgregor said:
Hey, the A7s holds up pretty well. A bit less DR. It's softer and maybe colors are a bit more digital. But for a $2500 mirrorless camera, it's not too bad. Also I didn't encounter any issues from the fact that the A7s shoots only in 8bit. (yes you just read that, so stop the nonsense about 8bit cameras being crap. Sure I'll take 10bit over 8bit, but 8bit is still good 99% of the times. HDcam and DVCproHD were both 8bit goddammit!).
Then of course the A7s strugles with massive rolling shutter issues and those ugly highlight edge artifacts...

highlight%20edge.jpg
Click to expand...
Are the ugly black highlight edges still there when recording to the external recorder?

Are any higher hdmi output resolutions besides 1080p60 available when in APS-C, 60fps mode?
 
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macgregor said:
Then of course the A7s strugles with massive rolling shutter issues and those ugly highlight edge artifacts...

highlight%20edge.jpg
Click to expand...

Just wow. For me this is definitely the most shocking part of your "review". I do not care that much about dynamic range, sharpness, colors etc, but this can be huge problem. Did you find workaround or does the camera makes this artifact all the time when shooting high contrast scene with backlit subject?

Anyway thanks for the tests!
 
thanks for the work macgregor!
does the a7s have better DR at 3200 on cine4 since its native ISO?

that highlight thing is a bummer
 
dspographer said:
Are the ugly black highlight edges still there when recording to the external recorder?

Are any higher hdmi output resolutions besides 1080p60 available when in APS-C, 60fps mode?
Click to expand...

The highlight aliasing occurs in every mode and recording externally. It doesn't occur shooting raw stills. I'm only keeping the A7s as a specialist low light tool and for production stills.
 
dcloud said:
thanks for the work macgregor!
does the a7s have better DR at 3200 on cine4 since its native ISO?

that highlight thing is a bummer
Click to expand...

I wouldn´t say the camera is 3200ISO native. I know this is confusing.
We should first define what "native" means. Is it the mode where the sensor receives no analog gain? Is it the mode with more DR? is it the mode with less noise?
I see it more like the way the red or alexa works. THe sensor is capable or registering a certain amount of stops of lights. Depending on where you map the mid gray you get more or less highlights/shadow distribution. And depending on where you map the mid gray you'll get a certain sensitivity.
 
squig said:
The highlight aliasing occurs in every mode and recording externally. It doesn't occur shooting raw stills. I'm only keeping the A7s as a specialist low light tool and for production stills.
Click to expand...

Some suggested that reducing sharpening helps. So, this does not seem to be true, right?
 
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