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Zeiss ZF 18mm f/3.5 Distagon MTF, Distortion, etc

The MTF graphs (below) look quite promising. Performance appears to be optimal wide open at f/3.5. The graphs shows a classic Zeiss Distagon “bulge”, at the ~18mm mark, suggesting some field curvature. For a thorough discussion of this phenomenon and how to interpret it, see Zeiss ZF Lenses. It will be very interesting to see how the ZF 18/3.5 compares to Nikon’s 14-24/2.8 zoom, and rest assured that my evaluation will be thorough. In the meantime, why not order Zeiss ZF Lenses, because if you want the detailed “scoop” on this exciting new optic, that’s where it will land. Get Zeiss ZF lenses at B&H Photo.

Zeiss ZF 18mm f/3.5 Distagon MTF @ f/3.5
(10, 20, 40 lp/mm)

The strong astigmatism for fine details (40 lp/mm) bears investigation for real pictures when the evaluation lens arrives. In prior testing on resolution charts, such astigmatism can be readily seen. Less clear is how much it matters on “3D” images.

Zeiss ZF 18mm f/3.5 Distagon MTF @ f/8
(10, 20, 40 lp/mm)

On an absolute basis, vignetting (below) is strong at f/3.5—approximately 2+ stops, but quite acceptable at f/8 (<1 stop). Such things should be kept in perspective however; this is an 18mm lens, and a lens design must trade some aspects of optical performance for others.

Zeiss ZF 18mm f/3.5 Distagon vignetting at f/3.5 and f/8

Distortion looks well-controlled for a lens of this type, but the wave pattern means it might be more difficult to correct in software. This should be a concern only for full-frame cameras; the “wave” rises outside the “DX” sensor size.

Zeiss ZF 18mm f/3.5 Distagon distortion (infinity)
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