A surprising new camera

 In this post a month ago I mentioned that I was considering two new cameras, a Sony A7r ii and an Olympus E-M1 III. In this post 10 days ago I wrote "So far it is going well enough with the A7ii that I'm not inclined towards the Olympus E-M1 III or the Sony A7rii at this stage. I'm going to put those possibilities on hold for now."  

I've gone further than that now; I really don't think either would work for me. 

As far as the A7rii goes, yes I could use larger apertures to get less diffraction softening than with the tiny apertures I'm using at the moment, but I would want to capture from further away and crop in order to get back the depth of field I had lost by using the larger aperture. With the image quality loss from a big crop (and it would have to be a big crop to make sense), I strongly suspect this approach would simply take me back to roughly where I am with the A7ii. And yes, I could use larger apertures to get better resolution, and put up with the reduced depth of field. But I know I wouldn't be happy with reduced depth of field, and in any case if I want to do this I can do it with the A7ii. All in all, I really don't think the A7rii would be useful for me.

And the Olympus E-M1 III? The potential benefit is with focus stacking for invertebrates using flash, for which none of my current kit is suitable, at least not for my preferred way of working - hand held. The thing is though, I am continuing to get results I like with tiny apertures, and finding that it works with subjects that are moving around, or on foliage that is blowing around in the breezes that are so common here, or grooming, or dealing with prey, or struggling to release themselves from a spider's web, or blowing bubbles ...... in fact anything that involves movement or action of some sort; those are the opportunities that attract me the most, and focus stacking isn't suitable for any of them. The more I think about it, the more I have to conclude that an E-M1 III would not be useful for me.

With my mind released from thinking about those two bits of kit it wandered off to a claim I had heard 8 months ago. It was in this thread that I started in the Photographic Science and Technology forum at dpreview.com. (Scary place, there are some fearsomely knowledgeable people there. It was the first time I had ever dared to post there.) I wanted to know whether, compared to my Sony A7ii, a camera with the same sensor size but fewer, larger pixels might be better for my purposes. This generated a lot of discussion, most of which I didn't understand, with much of it, as far as I could tell, not being relevant to my particular issue. 

However, in this post a fascinating possibility was raised. It was argued about, as to whether it was true or not, but I got the impression that the general idea was agreed by at least one person who is deeply knowledgeable about such things. The claim was (in my translation) that when dealing with an image captured at a low light level, what you can get out of post processing depends on how large the pixels are; the larger the better.

Now, my A7ii has a 24 megapixel sensor. In contrast, the Sony A7sii has half the number of pixels. Despite this, for a given scene and a given aperture and shutter speed (or in my case for a given aperture and flash level), both cameras will capture the same amount of light, and the image quality, the noise particularly, depends on the amount of light captured. 

However, post processing is done on individual pixels. Post processing involves arithmetic using floating point numbers. Each time a calculation is done for a pixel there will be one or more rounding errors. With repeated calculations these rounding errors will accumulate and the result may go further and further away from what it should be. Critically, the extent of this degradation depends on how good the data was that was captured by each pixel. 

Each pixel in the A7sii will capture twice as many photons as a pixel in the A7ii. There will therefore be a better starting point for the calculations, and the degradation will be less.

That at least is what I thought I could infer from those parts of the argument that I thought I understood. As you will gather from the way I phrased the previous sentence, I was by no means certain about this, but it did seem to make sense to me.

The thing is, because I use such small apertures I can't throw enough light on my scenes to get anywhere near using base ISO. I use quite high ISOs. This means that the camera is collecting less light than it would at base ISO, so even though I'm using flash I'm essentially working in a low light situation. And in addition to the low light, I use very strong post processing on my images to try to mitigate the effect of severe diffraction softening, and also to control highlights and bring up dark areas. Strong post processing very likely has a lot of potential for accumulating calculation errors and degrading the images. I couldn't help thinking that with an A7sii I might be able to get better results with the peculiar approach that I'm using. 

There is of course the fact that the A7sii is "only"12 megapixels. However, I know from experience with my bridge cameras that 12 megapixels is plenty for what I do, with my outputs being only 1300 pixels high. I sometimes do substantial cropping, but it isn't extreme and 12 megapixels is enough for the cropping I want to do. And in any case I seem to be cropping rather less with my new, tiny aperture approach with its greater than usual depth of field.

I idly wondered how much an A7sii would cost, so I went over to eBay to have a look. They looked affordable, and there was one with a low-ish shutter count (under 5,000) and less than 3 hours video capture, which is not much for a camera which is generally considered as a video camera rather than a stills camera. For £1,000 it also had an almost unused Sigma MC-11 Canon EF to Sony E mount converter. These are good. I have one. Having another would let me use non-Sony lenses on both the A7ii and the A7sii if I wanted. They cost around £200 new. And there were three batteries, two of which were Sony branded (around £50 each new). The seller had owned it all from new.

I bought it. 

It arrived very quickly, two days ago, and from the way it was packed I would guess that the owner was the type who looks after his kit very carefully (unlike me). 

The sensor was a bit spotty, but not as bad as I expected it to be. One wet clean got rid of most of the spots and I decided to leave it at that  and go and test it in the garden rather than trying to clean it more and risk getting it worse again and getting into a cleaning loop rather than getting out and testing it.

The A7sii has exactly the same body shape and button arrangement as the A7ii. I set it up in the same way as the A7ii. I used the Yongnuo flash setup that I had sorted out for the A7ii, described in the previous post.

There was not much around in the garden so I had a relatively short session of 40 minutes or so, but there was enough to show that the camera appeared to be working properly. I did notice one difference from the A7ii; I seemed to be getting stronger focus peaking signals, which made focusing easier. But perhaps it was just my imagination, seeing what I wanted to see from my new purchase. Anyway, the post processing went fine and the results certainly seemed no worse than with the A7ii. Perhaps they were a bit better, but that could have been my imagination too.

The 34 images ( a rather high 20% keeper rate) I kept from the 174  shots I captured during the session are in this album at Flickr. Here are several of them, including one natural light botanical shot from an interlude when I couldn't find any animals to photograph.

My first impressions, of handling, processing and outputs were promising.