Lens review: Nikkor 50mm f/1.4 AF D vs. Nikkor 50mm f/1.4 AFS G

I recently got the new Nikkor 50mm f/1.4 AFS G lens to replace my older 50mm f/1.4 AF-D Nikkor. Here is my initial review and comparison.

The Nikkor 50mm f/1.4 AFD (left) and its replacement, the Nikkor 50mm f/1.4 AFS G.

Specification Table:

MTF Charts (from nikon.com)

50mm f/1.4 AFD	50mm f/1.4 AFS

Build
Both of these two lenses are built very well.  The new 50mm lens has a much larger barrel and doesn't feel as "solid" as the AF-D model, but I think this is due to the way the outer barrel is constructed on the AF-S version.  Because the AFS lens is a "G" design, it has no aperture ring.  The AF-S version has a black finish that matches the finish on the D3, D300, and D700.  The new AFS version has the rubber gasket on the F-mount for weather sealing benefits.  Both lenses have an enclosed distance scale that goes from 0.45m to infinity.  The new 50mm has the traditional MA/M switch on the side of the barrel allowing users to go between autofocus (with manual override) to manual focus without having to engage a switch on the camera body.  The AFS version of this lens has a new optical formula, but note that it is not an internal focusing design.  This means that the lens elements will extend in and out as you focus.  One thing I found pleasant with the 50mm AFS is that the barrel is quite recessed, similar to my old 50mm f/1.8 Nikkor.  This designwill surely help shade the front element even if you are not using the supplied bayonnet hood.

Handling
The focus ring on the new Nikkor appears to be geared differently than the one on the AF-D model.  To go between 0.45m and infinity requires approximately a 180° turn of the ring.  Moreover, the AFS focus ring appears to be "geared down," in that there is not a 1:1 relationship between the rotation of the focus ring and the rotation of the lens barrel. The greater travel of the lens barrel and "geared down" focusing ring should be a benefit to manual focus operation.  Because the focus ring does not rotate when autofocus is engaged, the 50mm AFS is a little easier to handle during AF operation. The larger diameter body of the AFS lens also makes it easier to handle on today's larger DSLR bodies, such as the D3 and D700.

Autofocus performance
As with all AFS lenses, autofocusing is smooth and quiet.  However, due to the longer rotational distance that the focus barrel must travel, the 50mm AFS takes longer to go from minimum focus to infinity than its predecessor.  I timed AF performance on my D700 body.  The 50mm AFS required 0.8 seconds to travel from minimum focus to infinity.  The 50mm AFD only required 0.5s.  While some may find this disappointing, it is not entirely suprising-- the 50mm AFS is not an internal focus design as most of the other AFS Nikkor lenses are.  That means the entire lens barrel must be moved by the focus motor. Additionally, Nikon has clearly engineered this lens to be manual-focus friendly; the geared-down focus ring and greater travel means that manual focusing operation is far easier than on earlier AF designs.  In subjective testing, I found little practical difference in AF tracking speed between the AFS and AFD versions of this lens.  Both proved adept in focusing on my dog running straight at me. In theory, the AFS lens should perform better than the AFD version on lower-end Nikon bodies because the AF motor is independent of the camera. The AF motor in cameras like the D3 and D2 series is known to be more powerful than those in other Nikon bodies; further testing would be required to see if there are differences in performance between the D3 and say, the D80.

Image Quality
I produced a series of test shots with a Nikon D700 using matrix metering.  I captured all images in NEF format and then converted them to JPEG using their camera default settings in Capture NX 2.1.1. The 50mm AFS Nikkor shows improved image quality over the AFD version of this lens, especially when shot wide-open.  While both lenses have reduced contrast at f/1.4, the AFS version seems to do a little bit better in terms of overall sharpness.  By f/2.0, nearly all CA is gone on the AFS lens, while the AFD version still shows purple fringing until at least f/2.8.  (Note: because Capture NX applies CA removal automatically, results from in-camera JPEGs may vary.  I chose to leave CA removal ON in Capture NX because that is how I process my NEFs)  In my limited time with the 50mm AFS, I've noticed that bokeh seems slightly better than the AFD version. Background lines are slightly less harsh in the AFS lens, but the difference is very small.  The AFS version of this lens has overall better sharpness and contrast, especially at the edges of the frame, than the AFD version. In my tests, the AFS produced results at f/4.0 that were nearly as good as those at f/8 with the AFD version.

Conclusions
Both versions of the Nikkor 50mm f/1.4 lens are excellent.  Depending on the features you require, you may not find it necessary to spend the extra $155 to get the AFS version.  Despite the fact that the differences between these two lenses seem small, these small differences cannot be ignored. Having AFS focusing means full-time manual override.  If you like the 50mm focal length, and don't currently own the AFD version, I think the 50mm f/1.4 AFS G is a strong contender-- especially when you consider that you actually get a lens hood and rear lens cap when you purchase it (which would add another $30 to the price).  I will need to do some more testing of the AFS autofocus performance in active situations.  I was a bit surprised that the AFS lens didn't seem to focus faster than the AFD.  Of course, some of this is psychological perception.  The quiet focusing and longer focusing rotation on the AFS lens makes it feel slow, but my AF tests lead me to conclude that it tracks just as fast as the AFD lens.  If you are using a newer Nikon DSLR, especially one of the larger bodies, I think the larger diameter of the 50mm AFS lens is a plus.  The 58mm filter thread was an odd twist; most Nikkor primes in this range have a 52mm filter thread. If you have filters for an older 50mm Nikkor, you won't be able to use them on the new one.

Sample Images

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