First, please don't take any of this personally. I envy you photographic skills and the fact you get all these nice toys to play with
But I do have something to comment:
Quote: "
On the basis of these tests I would judge the A7s to have almost a three stop advantage over the A7r between ISO 6,400 (which is as high as I would use on the A7r) and ISO 51,200 where the A7s reaches its useful limit (for my type of shooting)."
A7r has about 50% quantum efficiency and the sensors are of similar size. Even if the read noise of the A7s is somewhat lower than that of A7r (which is likely on image level), outside of the areas with extremely little light (only a handful of photons per pixel), it would need to have several times higher QE than the ~50% of A7r to be as good as the article claims. This is of course impossible.
Additionally your test images don't agree with your text.
In practice what the above means is that throughout the usable range the midtones and highlights have similar quality, but in the very deepest shadows A7s likely have a slight advantage. (Of course in video there is dramatic difference as A7s doesn't skip pixels/lines.)
How the image data (ie. raw file) is processed of course plays big part. One should take advantage of the large pixel count of A7r and perform noise reduction before downsizing as downsizing alone is horribly inefficient way to doing NR. Downsizing is of course needed for comparison, just like you did, good!
Quote: "
They offer large pixels (greater dynamic range and colour depth)"
Large pixels offer large DR for the pixel,
but at the level of the image, which is the interest of photographers they typically offer lower DR. This is because signal and noise do not add up the same way (noise adds in quadrature). One needs to normalize the DR measurements for the same print size. The same goes for colour depth (whatever that means) and tonality and almost all metrics.
(On the other hand you did notice that there was no noticeable and/or significant difference between the DR of A7s and A7r which is likely correct.)
Quote: "
A significant addition to the A7s over its earlier siblings is an electronic front curtain shutter. This makes the camera completely silent"
A7 has EFC as well and it's not the feature which makes the camera silent. It's the full electonic shutter which is the reason (both curtains).
Two questions:I wonder about the silent mode:
how visible is the rolling shutter jollo effect for stills (I assume there is no global shutter, but only rolling one)
? This is very interesting feature regardless.
Is the viewfinder image better in low light than it is in the other A7-series cameras? I imagine this could be due to far superior live-feed from the sensor.
