FA* 300mm f4.5 jittery focus problem?

My F* 300mm f4.5 behaves the same way on my K5 (which has the same focus system as the K30).  It will snap to approximate focus and then "click clack" back and forth a couple times until it locks.    The K10D did the same thing, just a whole lot slower, so it didn't seem as "jittery."

I've got the FA*300 4.5 and the K-30 and I don't recognise these symptoms excepts as follows:

I find photographing birds in trees/grass or butterflies/insects in grass for example the af it not very positive and will flit between subject and background/foreground. This is in centre af and AF-C handheld, so I now switch to AF-S and and it locks onto the subject more often than not.

This is exactly what happens with my Tamron 70-300 LD Di and K-30.

My FA*300 was used extensively with my GX10 and K100D before this without those symptoms in those situations. I noticed it on the K-30 almost straight away as wildlife is what I shoot most. I figured it's just the price I have to pay for faster AF-C on pentax....

Other issues with AF-C and the FA* have cropped up when using auto and 5 point selection when it looses a subject (such as birds in flight) and is completely out of focus, it just sits there continually focusing back/forward's in a very short range, so jittery would probably describe that (again this happens with the tamron as well, and again this never happens on the GX10 or K100D). In single point AF-C this never happens. So it doesn't sound like the problems you describe, does it?

Thank you all for the comments and suggestions! I am less worried about the behaviour now. I will however give the contacts a good cleaning and see if it improves.

I still love this lens

Regards

W

I own this lens and the description of your AF-behaviour is on the spot with my lens too ;(

I asked the same question you did quite a while ago, but didn't get useful information.

If I use the lens on my K-r I do NOT have this issue... if i use it on my K5 and a K5 of a friend... same problem ;(

It's the same problem, I guess.. changing focus 3-5 times /second in a smaaaall amount, and realeasing when image is not always sharp... you hear it and you feel it, right?

I am using this lens more often in MF due to that reason... which is quite sad as I paid a hell a lot of money for a fast AF-Teleprime... images are awesome thought, tack-sharp and really colourful. not saturated, but...welll.... I like them.