Zeiss Batis 25mm f/2 Distagon: MTF Series from f/2 - f/16 + Distortion
Related: diffraction, distortion, optics, Sony, Sony A7, Sony A7 II, Sony mirrorless, Zeiss, Zeiss 25mm, Zeiss Batis, Zeiss Batis 25mm f/2, Zeiss Distagon, Zeiss Lenses, Zeiss mirrorless lenses
Get Zeiss Batis at B&H Photo.
The Batis line is a new lens line for Sony mirrorless cameras (Sony A7 series). See the general discussion of the Zeiss Batis lenses.
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.
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MTF
The MTF chart shows modest micro contrast at f/2. However, overall contrast is superb wide open, even into the corners, and that very high overall contrast is critical to visual impact of the image.
Most notable, the performance is exceptionally uniform at all apertures from center to corner. This is highly unusual for a 25mm lens.
Peak performance is at f/5.6, but f/4 will be nearly the same. Astigmatism can be seen, a property rarely absent in wide angle lenses.
Diffraction begins to assert itself at f/8, and 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.
Graphs courtesy of Carl Zeiss
Distortion
Distortion is typical for most wide angle designs in the 24/25mm range—about 1.5% with a mostly barrel distortion transitioning to pincushion at the edges and into the corners (“wave type distortion”).
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Graphs courtesy of Carl Zeiss
Vignetting
Vignetting to the extreme corner area is 2+ stops at f/2 without correction, and about 1.3 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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Graphs courtesy of Carl Zeiss
