Optical Performance and Quality
Now, we are entering the most interesting part of the review. How this 50mm f/1.2 Ai-S fixed focal lens with an optical design dating back to 1981 with no aspherical element or ELD glass performs with modern DSLRs. Nasim conducted Imatest tests that provide the most recent data about MTF Performance, Chromatic aberrations and Vignetting for this lens. Here is how it performed according to Imatest:
The results are astounding. This old 50mm f/1.2 beats the modern 50mm f/1.4G lens in the MTF performance in the center from f/2 to f/4 and equalizes it at f/5.6! So, its reputation for being the sharpest Nikon’s 50mm at f/2, thanks to its high performance, seems not overrated. Peak performance is reached at f/4.0 and the best overall performance is reached at f/5.6, where the lens shows very good sharpness throughout the frame. Contrast is really good and color rendition is superb.
Now, how the lens performs wide open, for which it’s the main reason to purchase this ultra-high-speed 50mm. Although the lens suffers from noticeable spherical aberration issues at the maximum aperture of f/1.2 and f/1.4 that lower the contrast and limit its performance across the frame, photographs show really good results in the center, where what is in focus is quite sharp:
For me, the weak corner performance at f/1.2 doesn’t matter because at this aperture, everything is out of focus except what it is intended to be. And even if the center is a little soft and has less contrast, it’s what gives the lens its strong appeal and makes images shot with this prime so attractive. But depending on the subject, the light and the distance from the subject, spherical aberration and coma can occur in a very specific way in what I call a “glowing effect” that gives an ethereal or “dreamy” look. Here is an example that shows this, shot at f/1.2:
Now compare the image to another one shot at f/2.0:
As you can see, stopping down makes the image appear completely different. Personally, I love the unique-looking images that you can get at f/1.2. This effect can be sought after, but it can also be undesirable. In those cases, changing the diaphragm to f/2 will surely get rid of most of the “glow”. But this can be the stumbling block for some that prevents from buying this lens.
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 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:
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:
And although vignetting is quite strong wide open, this feature contributes to one of the hallmarks of this lens. It can be used on purpose to give a more dramatic atmosphere to the photos or to emphasize the main subject. Or it can be easily corrected with Capture NX2 or other software.
Finally, to conclude, I want to quote what Michael Reichmann wrote in May 2012 in The Luminous Landscape about this lens: “This lens sings its most beautiful song wide open, where the combination of ultra-shallow depth of field, lovely bokeh due to its nine blade shutter, and coma along with CA allow for the creation of dreamlike images, with strongly out-of-focus backgrounds and foregrounds”. That says it all…
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