The first thing we noticed in testing the Nikon 50mm f/1.4G AF-S was that it was slower to autofocus than the AF-D model, which is mechanically coupled and driven by the focus motor in the camera body to which it's attached. Knowing that this fact would be of interest to our readers, we developed a quick test to determine how much slower.
Of great importance to this examination is the fact that we are seeking to test the performance of the lens, and not the camera that is conducting the autofocus operation on the lens. The autofocus systems between different Nikon bodies have different levels of performance. What we are looking for is the raw "torque" available to the lens, as a relative gauge of how the lens will perform in everyday focusing operations.
To accomplish this we decided to determine the time the lens took to focus between infinity to its minimum close focusing distance (approximately 45cm). The lens appears to operate at maximum speed when doing an unsuccessful focus operation (ie., the lens cap on), so we sought to determine this timing. Our method was comparatively simple: we recorded the sound of the lens focusing, and used a waveform sound editing program to determine the time between the two peaks representing the beginning and the end of the lens' focus travel.
We chose to measure the time between infinity and close-focus, rather than the complete focus cycle, because the delay between infinity -> close-focus and close-focus -> infinity was different between cameras, representing the strengths of the different focusing programs in each cameras. As well, the delay could be different between operations on the same camera. For the sake of transparency, we are including the complete cycle time in these results:
|Camera / Lens||Time|
|Time (full cycle)|
|D3 / 50mm /1.4D||0.28||0.72|
|D700 / 50mm /1.4D||0.28||0.73|
|D2x / 50mm /1.4D||0.29||0.74|
|D200 / 50mm /1.4D||0.32||0.76|
|F80 / 50mm /1.4D||0.41||1.09|
|D90 / 50mm /1.4D||0.42||1.04|
|D3 / 50mm /1.4G||0.69||1.54|
|D700 / 50mm /1.4G||0.69||1.55|
|D2x / 50mm /1.4G||0.69||1.58|
|D200 / 50mm /1.4G||0.69||1.58|
|D90 / 50mm /1.4G||0.69||1.58|
|F80 / 50mm /1.4G||0.69||1.60|
This test isn't meant to be definitive - there are plenty of ways we could poke holes in our own data - but it should give you a pretty good idea of how the 50mm f/1.4G AF-S performs, in comparison to the 50mm f/1.4 AF-D.
February 16, 2009