Pentax-DA 35mm F2.8 Macro Review
If this lens has one weakness it is the autofocus. When I initially purchased this lens, I thought it was defective. The problem occurs when you focus up close and then focus on a more distant subject; the autofocus seems unable to accurately focus. It cycles all the way in and then goes all the way out to focus on the subject. There is no rhyme or reason for this, and it happens at the strangest times. The DA 35mm does not seem to have a problem if the shots are all at the same general distance. In that situation it performs great. In fact, sometimes it is able to focus close and then further away without issue, but it is not consistent. I originally thought it was my camera, but it performed about the same with both the K200 and K7. I have found that one way to work around this issue is to let the lens cycle all the way in and then out. The other option is to use the Quick Shift feature to manually focus the lens and then let the autofocus fine tune the shot. In this situation, a focus limiter would be beneficial.
As previously mentioned the DA 35mm lens is designed as both a macro and a normal prime lens and the focus ring turns approximately 140 degrees from infinity to 1-to-1 magnification. Rather than continuing to rely on anecdotal information I decided to test the autofocus characteristics of the lens. For the test the focus ring was set at the various reproduction ratios. I then measured the autofocus response time to reach infinity. The test was completed a second time to measure the autofocus response time to reach 1-to-1 magnification beginning at infinity. From the test you can see that the autofocus takes 1.73 seconds on average to reach infinity from the 1-to-2 ratio. The 1-to-3 ratio on average takes a little over half a second to reach infinity. The 1-to-2 ratio response time is slower because the lens cycles all the way in first and then cycles all the way out to reach infinity. The autofocus response time to reach 1-to-1 magnification beginning at infinity is almost linear. The test was completed with a K7 and averaged response times, your results might vary.