Nikon NIKKOR 50mm f/1.2 Ai-S

MTF Performance

Here is how the lens performed according to Imatest:

The lens suffers from spherical aberration issues at the maximum aperture of f/1.2 and f/1.4, so its performance is quite limited across the frame. However, once stopped down to f/2.0, aberrations are dramatically reduced, resulting in much higher performance. By f/2.8, the lens yields excellent sharpness in the center and in the mid-frame. There is a little bit of focus shift when jumping between f/1.2, f/2 and f/4. Field curvature is definitely present, which explains the lower performance of the mid-frame and the corners when compared to the center.

Peak performance is reached at f/4.0, where the lens passes the 3600 mark in the center – sharper than the Sigma 35mm f/1.4 and sharper than any other Nikon lens that we have tested to date. Corners also pick up significantly by f/4. The best overall performance is reached at f/5.6, where the lens shows very good sharpness throughout the frame.

Distortion

Distortion is a little on the high side for a lens of this class. Imatest measured barrel distortion at -1.55. Unfortunately, since neither Lightroom nor Camera RAW have built-in lens profiles for this classic, all distortion corrections have to be carried out manually.

Chromatic Aberrations

Chromatic aberration levels are moderate. Imatest measured CA at about 1 pixel at the larger apertures, averaging 1.5 pixels at smaller apertures, as shown below:

Vignetting

As expected, vignetting is quite strong at the largest apertures, reaching as many as 2 full stops of difference in the corners. The good news is, vignetting is cut significantly at f/2.0 and practically disappears by f/2.8:

Here is an illustration of the worst case scenario, shot at f/1.2: