A Sony alpha 7S arrived yesterday for testing. Same origami box as the other alpha 7 cameras. Same lightweight documentation. Two nice differences: the a7S ships with two batteries and a battery charger. I guess they figure videographers will be going through batteries at a good clip.
In one sense, the arrival of the camera is timely; I’ve been doing simulations of large and small pixel cameras, and here is one with a modern large-pixel sensor. In another sense, it’s too soon; I haven’t finished the simulation work, and I’m in the process of recovering from a disk failure on my main computer. Not to mention the holiday weekend coming up. Mindful of the interest in this camera, I’m going to press ahead on all fronts.
I’m curious about several aspects of the a7S:
- What are the characteristics of the sensor with respect to the ISO setting? Other reviewers have indicated that the camera is not “ISO-less”. I’d like to find out for myself. The camera is not (quite) ISO-less. Images here.
- How much aliasing and false color do we get with sharp lenses focused on big pixels? What kind of antialiasing filter does Sony have on this camera? Images here.
- How well does the camera work in fully electronic shutter mode? We know it won’t be able to tolerate a lot, but can it tolerate a little camera or subject motion? Test results here.
- What games has Sony played with the raw files and the analog to digital converter settings? We can expect the Sony raw compression scheme, but is it changed in what people are saying is a camera with a 14+ bit engineering dynamic range? I don’t see how the old 13 bit to 11 bit to 8 bit delta modulation scheme could support that much DR. [Added 7/17: From examining the file sizes, it looks like the A7S uses the same raw compression algorithm as the a7 and a7R.]
- What is the intra-scene DR under various conditions (and various definitions of DR)? Read-noise-limited DR information is here. Read noise vs shutter speed information is here. Photon-noise limited-DR information is here. How about the inter-scene DR, assuming the camera is not ISO-less? It in indeed greater than the intra-scene DR.
- How does the large pixel sensor fare with third party symmetric wide-angle lenses like those made for the Leica M-series cameras? It should be better than the a7R and the a7 with respect to corner smearing and color casts. Zeiss 35mm f/2 Biogon in the Leica M-series mount. Leica 16-18-21mm f/4 Tri-Elmar ASPH. Leica 28mm f/2.8 Elmarit ASPH. Leica 50 mm f/1.4 Summilux ASPH. Leica 24mm f/3.8 Elmar-M ASPH. Leica 18mm f/3.4 Super-Elmar-M ASPH. Summary.
Plenty to work on.
Jim, please do not forget to test raws with
1) rolling electronic shutter – both single shot and multishot modes (like when you press release once to make a sequence for bracketing)
2) and the same for a regular mechanical shutter – does A7s have differences in raw between single shot and multishot modes (like when you press release once to make a sequence for bracketing) – you found that prev. A7 models did
Thank you !
The answer to 2) is, yes it does. 13 bits in single shot, and 12 bits in continuous. In full electronic shutter mode, it appears at first blush to be 12 bits at low ISO, with some funny combing making it effectively 11 bits or less as the ISO goes up..
what is the effective time that takes A7s to do grab the frame in rolling electronic shutter mode for stills ? is it like 1/20s, 1/30s ? if you can test this too please
OK, I’ll do that. Dont’ know quite how right now. Probably with an oscilloscope.
I am curious if the A7s shows less vignetting with wide angle lenses then its higher resolution brethren. I would assume the high resolution sensors have relatively deep wells, so they would lose more oblique light. Is there any evidence to support this notion?
> I would assume the high resolution sensors have relatively deep wells,
I guess the issue is not about the “depth” (technically the depth in silicone for a given state of the chip creating technology shall be the around the same), but about the size of surface areas for microlenses, CFAs under them and what lays on/in chip itself under CFAs through which the light gets to where it creates the charge
If the depth stays the same and the size of the pixel viewed normal to the chip surface gets smaller, the percentage of the pixel open to shading by the edge for oblique rays gets larger, even if the absolute amount gets smaller. I think that’s what the poster meant by “relatively deep”. Although, as you hint, the microlenses may be the long pole in the tent.
Sure looks like it. No corner smear to speak of, either. Hardly any color cast.
> How well does the camera work in fully electronic shutter mode?
So far so good for me but I would love to have been able to assign that function to one of the custom keys, or at least to a slot in the quick Fn menu. Unfortunately, you have to go look for it in the full menu to turn it on and off. Rolling shutter would be one reason to turn it off (I haven’t really noticed it so far), but more annoyingly (for me), the silent mode also disables some useful functions like exposure bracketing (i.e. HDR).