Nikkor AF 20mm f/2.8 D - Review / Test Report - Analysis
Lens Reviews - Nikon / Nikkor (APS-C)
Article Index
Introduction
Analysis

Distortion

The AF 20mm f/2D exhibits a very pronounced degree (2.3%) of barrel distortion which can be quite noticeable in real-world scenes. This is a little disappointing for a fix-focal because it does not perform any better than an average APS-C standard zoom here.

The chart above has a real-world size of about 120x80cm.

Vignetting

The AF 20mm f/2.8 D is a full frame lens thus enjoying a sweet spot advantage on APS-C DSLRs. Nonetheless the vignetting at wide-open aperture is very high at 1.36EV which will be noticeable in some situations. From f/4 and up the problem is well controlled for a (native) ultra-wide lens though.

MTF (resolution)

The Nikkor didn't really convince in the resolution tests. The center performance is very good to excellent and the borders follow closely. However, the extreme corners fall apart in quality reaching only good figures at medium aperture settings. It's interesting that the Canon EF 20mm f/2.8 USM showed a similar behavior though to a lesser degree (better extreme corners). In both cases this is a bit disappointing especially when taking the full frame design into account - seems as if the projection characteristic of these legacy lenses isn't really perfect for today's image sensors which prefer a perpendicular path of rays. The performance of the tested sample was very symmetrical so it didn't seem to be a bad sample.

Below is a simplified summary of the formal findings. The chart shows line widths per picture height (LW/PH) which can be taken as a measure for sharpness. If you want to know more about the MTF50 figures you may check out the corresponding Imatest Explanations

Chromatic Aberrations (CAs)

Chromatic aberrations (color shadows at harsh contrast transitions) are pretty bad especially for a fix-focal. With an average CA width of around 2x at the image borders the Nikkor is among the worst fix-focals tested so far.

Verdict

The Nikkor AF 20mm f/2.8 D had a very good reputation during the film era but the D200 didn't really like the lens. The resolution is fine for most of the APS-C image frame but the extreme corners never really reach impressive results even at medium aperture settings. Vignetting is fairly high at f/2.8 and CAs are pretty bad. All-in-all you may prefer to look elsewhere to cover this focal length on an APS-C DSLR.

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