I was in a situation similar to the opening post – I’d bought a second hand DA* 50-135 that was about six days out of its manu’ warranty and the autofocus died completely. I expressed my disappointment to Pentax Cust Servs and they kindly paid for the repair. The lens was great for about six months, then the same problem of erratic autofocus began to recur – sometimes it would work, sometimes it would not.

I was going to send it to Photopia for another service but then, recently, during the covid thing, with a bit of spare time at home, I decided to try and figure out what the conditions had to be for it to work.

I just used it over and over, sometimes in manual sometimes in auto, until it began to work. And then it would stop working and I’d repeat the process.

Eventually, I think just because I was using it often, it became more reliable – and now it seems to work perfectly all the time. And so now, at least twice a day I point the lens at some plain sky and force it to hunt to its limit in both directions, then focus on a range of different objects around the place at different distances.

I seems like just using it regularly keeps it loosened up and ready to go !

Thought I’d mention this here so if anyone gets the problem of erratic autofocus, they can try just using the lens more often – see if that simple solution fixes the problem, before paying for a service!

Cheers
Deck Chair Dave

Thank you to Cedricd for comments also... so from what you say, a K1 using a DA* lens in cropped mode is producing BETTER images than a K3 using the same lens; even though the DA* lens is optimised to work with the APS-C sensor in the K3. That certainly gives me food for thought.
I think I will delay upgrading my camera body until I'm closer to having the funds available for a K1.
deck_chair_dave

Many thanks for all replies - very helpful.
I have a couple of full-frame lenses, a 50mm and a 100mm, but I do like using the zooms.

I would like a K1, but I think pound for pound I might be better off using my DA* lenses on a K3.

Many thanks for your help.
deck_chair_dave

Hi Folks!
Has anyone had experience of using DA* lenses with a K1 ?

I have a DA* 16-50mm and DA* 50-135mm which I’ve been using on a K10D.
I’m thinking of upgrading to either a K3 or a K1.

I know the DA* lenses are designed for use with the APS-C sized sensor used in both the K10D and the K3.
Are there any issues using these lenses with the K1s full-frame sensor ?

Best Regards to all..

I’m currently not subscribed, and I don’t think I would subscribe if the magazine were pdf only.

Having pdfs available for back-numbers at a modest cost is great.

Having pdfs available to non-members at modest cost could be a great way to encourage more people to take a subscription.

A pdf library of technical articles would be very good.
A kind of on-line reference database for all things Pentax.

Cheers

Hello, Thanks again guys for your comments.

I had come across comments elsewhere on the web that the SDM could fail, and that sometimes the failure was gradual - and I jumped to the conclusion that the hunting was the first sign of a failing motor.

I've just been looking at the lens again.
The SDM seems to be working smoothly and following your comments I tried the lens on my MZ-S and it did not hunt at all, in fact the focus was very quick.

The hunting only seems to occur when I put the 50-135 on my K10D.

I will try and test the lens on another K10D, and then most likely, send the lens to JP Solutions.

Thanks again guys.
Alan (D_C_D)

Hi Stefan, Thanks for your comments. I have a DA* 16-50mm that works fine on the same camera (K10D). So I think this 50-135 might have a problem with the SDM.
It's a shame, the lens is not very old.

Kind regards
Alan
(deck_chair_dave)

Hi All,
I have a second-hand DA* 50-135mm that has developed a problem - most occasions it just cannot find focus, it just hunts in and out.
I've heard this is not an uncommon issue with this lens.
Anyone had similar experience ?

A couple of years ago I sent an MZ-S body to Pentax for repair and the service was very poor, so I'm wary of where I might send this lens for attention.
Anyone able to comment on reliable repair centres for Pentax lenses in the UK ?

Best Regards
D_C_D