HD Pentax-D FA* 85mm F1.4 ED SDM AW
The D FA* 85mm uses a modern autofocus system, with the most recent incarnation of Pentax’s SDM motor. The lens lacks the mechanical screw-drive coupling required for use with older camera bodies, but will work with cameras dating from the K10D (2006) or more recent (the same cannot be said of the aperture control, which requires a K-50 or more recent camera to operate properly).
The AF system is almost inaudible even in a silent environment. This is on par with the D FA* 50mm and the D FA 70-210mm, being among the best incarnations of a silent AF drive we have seen. Focusing is internal and the length of the lens remains constant. The focus ring does not rotate as the lens focuses, and the front element does not rotate.
The AF is generally accurate and responsive, with a feeling of speed and decisiveness.
The lens allows quick-shift for manual AF override at any moment.
The lens includes one switch on the side, an AF-MF toggle.
Live view focusing feels just as responsive and decisive as using the viewfinder. There doesn’t seem to be a difference from a user’s perspective.
Manual focus with the 85mm is pleasant, thanks to the wide focus ring taking up a large chunk of the lens' body. This focus ring has an excellent level of friction and good dampening. There is no backlash when reversing the direction. The ring has a throw just shy of a half-turn, being closer to 165°.
The lens goes above our expectations regarding manual focus.
We tested the AF speed with a Pentax K-1 II, using both live view (contrast-detect AF) and the viewfinder (phase-detect AF). The subject was a black cross on a white background, about 1.5 meters in front of the camera. We used the central focus point. We set the lens at infinity before each test, and three measurements were averaged for each data point. Measurements were performed by recording the AF noise, at various levels of ambient light.
For reference, the Pentax K-1 II's autofocus sensor is rated for ambient light levels as low as -3 EV.
Note that 5 EV corresponds roughly to a small room lit with a 60 W bulb, and a sunny day corresponds to 16 EV, and a moonlit night to -2 EV.
In our tests, the D FA* 85mm performed close to the best we ever tested. In fact, it is even faster than the D FA 70-210mm (a lens which impressed us tremendously), particularly when light levels are low. It is also faster than the DA* 11-18mm, another lens with surprisingly fast AF speed.
At very low light levels, using live view or the viewfinder doesn't make much of a difference. As things get brighter, phase detection through the viewfinder gets progressively faster than live view, but both are very fast.
In conditions that would be considered dim by all accounts (as low as 3 EV) AF speed gets below 0.2 seconds using phase detection. In other words, focus is near instant.
We must commend Pentax on the huge progress they have made regarding AF in recent years. It seems that each time a new lens is released, AF speed is improved. We are actually surprised that the company does not showcase these improvements more strongly, as they are certainly worthy of note.
Remember that actual speeds will vary greatly with the subject and lighting conditions.
We experienced almost no occurrences of hunting with the 85mm during our tests. The only hunting we saw was under a starlit night sky, with no light sources close-by. In adequate to good light, there was no hunting in any of our tests.
The Pentax D FA* 85mm offers splendid AF speeds and accuracy. It belongs with other recent Pentax lenses, illustrating the giant leaps the company made in the last few years.