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Sony a7r vs a7S (shooting RAW stills)

 
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I tested the Sony a7r and a7r, looking at sharpness, dynamic range, and high-ISO performance.

Summary: the a7r is sharper, the a7S noise advantage is about one stop but only appears at very high ISO values, and the a7r has a DR advantage of around 0.66 stops at ISO 100.

Bonus: my vintage Leica Elmarit-R 35mm f/2.8 from 1978 is sharper than the Sony FE 24-70mm f/4.0 set at 35mm.

High-ISO performance

After downsampling the a7r images down to 12 Mpix, the a7S still holds an advantage of one stop at very high ISO values: ISO 25600 on the a7S looks about the same as ISO 12800 on the a7r. But none of them looks great, and the difference goes away as you bring down the ISO.
ISO 12800 on the a7S looks slightly worse than ISO 6400 on the a7r, so the difference there is already less than a stop. And by ISO 3200 or lower, both are perfectly usable, and the a7r has the sharpness advantage.

standard: a7S 25600 - mouseover: a7r 12800
both: Leica 35mm f/2.8 set at f/8.0 and with 9-stops ND filter,
speed set for correct exposure, center 100% crop from 12 Mpix image



standard: a7S 12800 - mouseover: a7r 6400
both: Leica 35mm f/2.8 set at f/8.0 and with 9-stops ND filter,
speed set for correct exposure, center 100% crop from 12 Mpix image



standard: a7S 3200 - mouseover: a7r 3200
both: Leica 35mm f/2.8 set at f/8.0 and with 9-stops ND filter,
speed set for correct exposure, center 100% crop from 12 Mpix image





Dynamic Range

At ISO 100, both cameras seem to have approximately the same headroom in the highlights: I overexposed the shot by up to 3.3 stops, and still could get the clouds back perfectly, but they were close to clipping in both cameras. But the a7r can dig farther into the shadows, by around 0.66 stops: the shot that is underexposed by 5 stops on the a7r is just slightly worse than the one that was underexposed by 4 stops on the a7S (I bring them back to correct exposure in post; all shots with no noise reduction or post sharnening). Same for 6 and 5 stops, and for 4 and 3 stops.

standard: a7S underexposed 3 stops - mouseover: a7r underexposed 3 stops
both: Leica 35mm f/2.8 set at f/5.6, center 100% crop from 12 Mpix image



standard: a7S underexposed 4 stops - mouseover: a7r underexposed 4 stops
both: Leica 35mm f/2.8 set at f/5.6, center 100% crop from 12 Mpix image



standard: a7S underexposed 5 stops - mouseover: a7r underexposed 5 stops
both: Leica 35mm f/2.8 set at f/5.6, center 100% crop from 12 Mpix image



standard: a7S underexposed 3 stops - mouseover: a7r underexposed 4 stops
both: Leica 35mm f/2.8 set at f/5.6, center 100% crop from 12 Mpix image



standard: a7S underexposed 4 stops - mouseover: a7r underexposed 5 stops
both: Leica 35mm f/2.8 set at f/5.6, center 100% crop from 12 Mpix image



standard: a7S underexposed 5 stops - mouseover: a7r underexposed 6 stops
both: Leica 35mm f/2.8 set at f/5.6, center 100% crop from 12 Mpix image





Sharpness

With its 36 Mpix, the a7r is obviously sharper than the 12 Mpix a7S, even when the a7r is downsampled to 12 Mpix, or, even more strikingly, when the a7S is upsampled to 36 Mpix (all shots with no noise reduction or post sharnening).

standard: a7S - mouseover: a7r
both: Leica 35mm f/2.8 set at f/5.6 (100% crop from 12 Mpix image)



standard: a7S - mouseover: a7r
both: Leica 35mm f/2.8 set at f/5.6 (100% crop from 36 Mpix image)



That was easy to expect. So I played a bit more, comparing my vintage Leica Elmarit-R 35mm f/2.8 (from 1978) with the Sony FE 24-70mm f/4. The Leica is clearly sharper at f/4, both in the center and in the corners. At f/5.6, the Leica vintage prime is still sharper than the Sony modern zoom but the difference is smaller.

standard: Leica 35mm - mouseover: Sony 24-70mm f/4.0
both at 35mm f/4 on a7r (100% center crops from 36 Mpix image)



standard: Leica 35mm - mouseover: Sony 24-70mm f/4.0
both at 35mm f/5.6 on a7r (100% center crops from 36 Mpix image)



standard: Leica 35mm - mouseover: Sony 24-70mm f/4.0
both at 35mm f/4 on a7S (100% corner crops from 12 Mpix image)
(I screwed the framing in one of the a7r shots, that's why I use a7S for the corners)



standard: Leica 35mm - mouseover: Sony 24-70mm f/4.0
both at 35mm f/5.6 on a7S (100% corner crops from 12 Mpix image)



Now, a7r with Sony 24-70mm, or a7S with Leica 35mm? Well, even at f/4 and downsampled to 12 Mpix, the a7r still wins, at least in the center. On the corner it should be a much closer call, but I can't really say, because I screwed up the framing in the a7r f/4.0 shot and can't compare corners, just center.

standard: a7S Leica 35mm - mouseover: a7r 24-70mm
both at 35mm f/4 (100% center crops from 12 Mpix image)






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