Pentax K-3 review – Autofocus
The K-3 is equipped with a respectable 27-point AF system, and 25 of these are the more sensitive cross-type points. The number of AF points is reasonable, with all of them placed around the centre of the frame. Naturally, I used the camera with a few different lenses. Of these I found that the Pentax 40mm f/2.8 Limited lens was the fastest to focus. It was fairly snappy in single-shot spot AF mode. However, as we have seen, or should I say heard before, the AF is quite noisy with Pentax DSLRs, particularly when using the kit lens.
Although quite fast, the AF feels a little slower than it actually is due to the process being fairly audible. Although the action of focusing appears to happen in one motion, the noise emitted from the motors tells us that the lens seems to roughly focus and then fine-tune.
The 18-55mm f/3.5-5.6 kit lens isn’t especially fast, but is a satisfactory accompaniment for those starting off with the camera, especially given that it is waterproof. Switching to the 60-250mm f/4 lens, the performance is again steady without being snappy. Photographing wildlife using continuous AF, the K-3 was able to keep up with trotting deer, although with a few shots where the focus was slightly off.
Perhaps the best summary of the AF system is that it isn’t sleek. While in good light it finds focus quickly, it is not blazingly fast and in dim light it does slow down. Those wanting to shoot wildlife or fast-moving subjects will find the AF speed a little frustrating. While it is possible to get shots in focus, don’t expect a high success rate.