Here’s a quick comparison of the Sony a7R II and a7S II as far as resolution is concerned (shot with the 28-70mm OSS zoom):
Sony a7R II Full frame vs APS-C mode
First, since the a7S II can’t shoot 4K in APS-C mode, here’s a comparison of APS-C vs FF on the a7R II:
To my eyes, it’s too close to call. The sensor is bigger, but the internal computer does a great job on both.
Sony a7R II vs a7S II Full frame
Here are the images (converted to JPEG, but in full resolution):
To my eyes the a7R II has a slight resolution advantage, but it’s very close.
Sony a7R II vs a7S II Full frame ClearImage Zoom 1.5x
Here are the images (converted to JPEG, but in full resolution):
Here you can see the a7R II has an advantage.
Sony a7R II vs a7S II Full frame Digital Zoom 4x
Here are the images (converted to JPEG, but in full resolution):
Here you can see the a7R II has a definite advantage!
Verdict
What do I think? The a7R II has higher resolution than the a7S II. However, the a7S II is a 1:1 sensor, so it’s good enough to compete with the best.
The advantage the a7R II has is, you can punch in and still hold resolution. One negative is, some people have reported aliasing with the a7R II, though as you can see elsewhere, I’ve shot it with the best lens (the Otus 55mm f/1.4), and didn’t see any.
