FA* 300mm f4.5 jittery focus problem?

Started 11 months ago | Questions thread
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WalterS
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FA* 300mm f4.5 jittery focus problem?
11 months ago

Hi everybody (that owns this lens)...

I am wondering if my lens needs repair or service.

I havent used the FA* 300mm f4.5 lens in a while, but used it on a K-30 last weekend. And it was annoyingly "jittery". I mean the camera would "change its mind" on where to lock focus very often (fractions of seconds). Sometimes it would not settle at all. This was very small increments - not hunting between close and infinity focus lock. It was so bad that I missed quite a few shots.

More details:

  • Bright sunny morning (in Africa) trying to focus on birds about 2-5 meters away, on an evenly coloured grass patch or sometimes in trees nearby. Birds were close enough to fill large part of the viewfinder.
  • I was hand holding, but I am a generally steady shooter.
  • I changed the auto-focus settings to centre spot only (tried auto 5 and 11 points also - worse results). Obviously using single shot auto-focus (not AF-C).
  • Tried the lens on my old *ist ds camera and it was much the same - just slower (which was actually better in this case).
  • Other auto-focus lenses were working normally on both cameras.

Perhaps the screwdrive on the lens has worn-out?? It has seen a lot of use after all. Or is it just the way it behaves on these newer Pentax bodies?

1/640sec @ f4.5 iso1600 with K-30. Straight from camera jpeg.

At least some shots were in focus!

Cheers

Walter

ANSWER:
This question has not been answered yet.
Pentax *ist DS Pentax K-30
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