Originally posted by luftfluss IIRC, when the Japanese press reviewed the K-3 III weeks ago, they used the DA* 50-135 and found the AF performance to be quite decent - perhaps even surprisingly so.
Come think of it, the thing with the DA*50-135 is that it has a very long focus throw, which means it suffers much more than others when it starts moving up and down to find focus (esp when hunting). I suspect that when it would snap to correct focus immediately, the effect of the longer focus throw would be much less. Especially if the previous subject photographed is at more or less the same distance as the new shot.
I imagine in case of focus tracking the effect would be massive. On previous cameras once it lost the subject it focused on the background and simply never had the time to move back to the correct position because of way too long a turn to do so. If the new AF can help it keep up with small adjustments (I'm sure it's fast enough for that) without losing the subject, that would make a difference for this lens more than other lenses that might have been capable of getting the subject back on previous cameras.
Probably the gain will be both for SDM survivors and screw drive converted ones.