I rented a Sony A7S to take with me over Labor Day on my trip to the Lost Mesa for night images. I had read Ian Norman's review at Lonely Speck and thought it would be fun to see how a camera can shoot at ISO 51,200 does in the field. Ian gets into the technical side. I will stick to mostly the user experience and results.
The moon phase was past the new moon but I was hoping it would still be a thin enough crescent to be able to photograph in the evening after sunset. I knew the moon would set around midnight so early morning would be dark and I hoped the Milky Way might be in a good spot for a few locations I had wanted to do some night photography at.
My camera set up for this trip would be my full frame Canon 5D Mark II, my crop (APS) sensor Sony NEX6, and the rented full frame Sony A7S. Because there are few full frame NEX mount lenses I also rented the Metabones adapter allowing me to use my Canon mount lenses on the Sony.
I had two lenses I could alternate between the full frame 5D2 and A7S. The Bower 14mm f/2.8 and the Bower 24mm f/1.4 (both really Samyangs under the Bower brand) are both really great lenses, sharp, excellent at night, and cheap. On the Cropped sensor NEX6 I would be using the Rokinon (also a Samyang) 8mm fisheye. This is a NEX mount specific lens that is tiny, sharp, and cheap.
All three lenses are very good wide open and at night with low coma.
In the field I found the quarter of a moon was already so bright it was casting a shadow on the dark open range country of the Lost Mesa. I photographed at night after sunset but knew it would be better in the predawn dark. I was using all three cameras-each set up on a tripod.
Night is the only time to try three cameras as the longer exposures all you to move from camera to camera. It was do-able although I was always moving.
The Canon and NEX6 are second nature to me. I know each one very well and even though they are very different I am comfortable working with both-even in the dark. The Sony A7S has some similarities to the NEX6 so it was pretty easy to adapt to it. Overall it has some good simple analog controls. Having said that, there were still some settings that I did not make the adjustment to very easy in the few days I had the camera. So from a control standpoint its good but I think it could be better.
The NEX6 and A7S are also very similar in the size of the camera body. Both are small. The big difference is the lenses. The NEX6 has some dedicated lenses that are tiny. The kit lens is a 24-75 and collapses to make it tiny and easily pocketable. Even the fisheye is small-like a shot glass. The A7S does not have dedicated lenses I need so I was able to adapt my Canon lenses but you then end up with a camera and lens that really is only marginally smaller than my 5D2 setup.
See the example here. The Samyang 24mm and Canon 17-40 are very similar in size. As you can see with the adapter you gain very little in in a size advantage. In fact you now have a rather front heavy camera. Just look at the NEX6 to see what you can do. Granted a full frame lens will be bigger than this, but it should still be significantly smaller than a DSLR lens. This is the big "issue" for this camera right now-it needs dedicated not adapted lenses.
The images this combo produced were great. However, I think that the full frame NEX models will not come into their own until Sony and Samyang start producing some dedicated lenses for it that are small.
The difference in size between the Samyang fisheye for a crop sensor DSLR and the crop sensor NEX is significant. If they can make a similar size reduction for the full frame cameras you will really have something.
Image quality out of the A7S was very good. It had the lowest pixel count but the best high ISO performance. I typically shoot the 5D2 and NEX6 at ISO 6400 at night. Both are just starting to reach into noisy territory but the increase in light gathering makes it work. On rare occasions I will push each to 12,800 (where images only work some of the time)but 6400 is my normal setting.
With the A7S ISO 25,600 looks as good as ISO 1600 or 3200 on either of my other cameras. I even shot at ISO 51,200. Both looked pretty good, although I think I would stick to ISO 25,600. Gives you extra light gathering capabilities and also allowed a shorter exposure for sharper stars. At ISO 51,200 the biggest thing is not the noise.....but blowing out the sky. That's right, you have to go short on the exposures or you will blow out the Milky Way. Did you ever think you would hear that about night photography?
In the early morning darkness I was back out making images. The A7S with 14mm and NEX6 with fisheye for images of petroglyphs and the Milky Way.
Here I also did a test of putting the Fisheye lens (a cropped sensor lens) on the full frame A7S since they are both the same lens mount. Obviously the image only filled the central portion of the frame but when cropped down gave me a chance to use the fisheye at the high ISO capability of the A7S. The images have a similar look to the NEX6 but you have significantly fewer megapixels to work with. See those images at the top.
I also spent a night on this trip at Guadalupe Mountains National Park. I wanted to try some shots of the prominent cliffs that make up El Capitan and the south end of the Guadalupes. I again shot all three cameras and worked at a variety of ISO on the A7S. Here is a comparison of a few.
Again, I was impressed with what the A7S could do and that you could get a 2 stop advantage over the 5D2. That two stops gives you more light gathering ability and therefore more stars. It also makes a difference in allowing shorter exposures. That helps eliminate star trails and lets you make more images over the course of the night.
I use the 450 rule. By that my 14mm should be able to do a 32 second exposure or so without star trails. I usually shoot 30 second exposures and at extreme closeup there are trails forming. ISO 25,600 would let you do 15 second exposures and help eliminate them.
So after a long weekend how does the A7 fare? Pretty good. The camera is another winner from Sony. What holds it back is lack of small prime lenses. When Samyang and Sony start making them, this becomes a real option. Until then you are buying this solely for high ISO where it has significantly better capabilities than the 5D Mark II and even holds an edge on the 6D.