Get Zeiss Batis at B&H Photo.
I expect to have the Zeiss Batis 25/2 Distagon and Zeiss Batis 85/1.8 Sonnar in for extensive field testing sometime in June. Coverage will go into Guide to Mirrorless.
The MTF chart shows excellent micro contrast wide open at f/1.8 with highly uniform sharpness corner to corner at all apertures. Overall contrast is superb wide open, even into the corners.
Peak performance is reached at center by f/2.8, but the variation (wave inflection) across the field looks to be a mild field curvature; stopping down a bit more delivers outstanding micro contrast at f/5.6, far exceeding most lenses and no less good than the very best Leica M lens. Minor astigmatism is present.
Diffraction drops contrast overall and for fine detail at f/8 (in effect what one hopes to see, indicating an excellent performer). By f/11 its effects are quite dulling. At f/16, the performance becomes much inferior to f/16. See Mitigating Micro Contrast Losses from Diffraction Blur in MSI. These behaviors are all expected and good in this sense: a lens that shows little effect from diffraction is not very good to begin with! In other words, the better the lens, the more diffraction throws a wet blanket onto performance.
Some pincushion distortion is typical for medium telephoto lenses, buy this level of distortion when uncorrected will be very noticeable. By comparison, the Zeiss 85mm f/1.4 APO-Planar has distortion so close to zero it can be called distortion-free, and the Zeiss 85mm f/1.4 Planar has about 0.2% distortion—about 15X less than the Batis 85/1.8. All lens designs are compromises, so it seems that distortion was traded off for uniformly high sharpness and a smaller/lighter design, knowing that the camera can correct for it automatically (or the raw converter).
To my eye, pincushion distortion is visually troublesome compared to barrel distortion, and this 3% pincushion distortion is unacceptable for many purposes if not corrected: skylines, buildings, etc would bow upwards, and filling the frame with a face is not going to look flattering—so plan on enabling distortion correction for the 85/1.8 Sonnar.
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Vignetting to the extreme corner area is 2+ stops at f/1.8 without correction, and about 1.25 stops with correction. I’m generally not a fan of vignetting corrections, since vignetting is also a creative tool. It is potentially worrisome for gradient transitions, but if the camera does the correction in 14-bits internally (before the Sony 11+7 lossy compression file is saved), then it should nearly always be just fine.
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