AF problem on Pentax 18-135

I recently acquired a 18 - 135mm Pentax lens as a walk about lens. There seems to be a problem with the AF It won't auto focus when used between 18 and 35mm. Above that it is fine. I have two K5 bodies and it has the same problem with both bodies so I have to assume that the lens is at fault. I have no problem with manual focus only when set on AF and only between 18mm and around 35mm. Has anyone else encountered this problem?

Cheers Dave

Are you using any filters? I could not get mine to autofocus properly with a polariser.

Hi, thanks for the reply.
The only filter in use is a UV filter mainly for front element protection

Dave

Try it without the filter. If it then works ok, join the debate over whether or not a filter is the best way to protect the front lens element!

I have tried without filter but to no avail. Still auto focusing above 35mm but not between 18mm and around 35mm. This has got me stumped.

If there's a fault, then return for an exchange or repair seems the only way to go.

hello,
just to say i got the same problem on my 18-135 :
between 18 and 24 the lense can't focus at a distance over 2 meters, under this distance, it works better,
when the subject is in dark light, the autofocus works better !!!
it seems that the IQ is very poor at this range

did "digitalKitchen" sent his lens for repairing and was it successful ?

He only ever posted those three comments in this thread so guess we'll never know unless your post generates a new comment email to him and he responds again. Perhaps he returned it and you've got it now!
Has it just gone like this? Also, is it OK when manually focussing?
While John Riley's suggestion seems the way to go still, it might be worth seeing if cleaning the contacts on the lens and camera body help first. If the lens has just got sluggish, a good workout might bring it back to life if its the SDM motor struggling. It could, perhaps, have got some grit trapped preventing it working smoothly and a workout might free it.

thanks Jack for your response,
it's impossible to focus manually when automatic don't succeed
in my case it's not a contact issue.
it seems to me that the manual focus ring cramp the automatic focus mecanism, as I feel the ring moving when autoatic focus doe's not work
when it's ok, the ring does not rotate at al.
l

Doesn't sound like something you can fix yourself unless you have skills in that area, but suspect if you have you wouldn't be asking! I can't recommend a repairer as I have no idea as to your location.

Just to check it isn't something else (e.g. a camera problem) do other lenses work OK? Alternatively can you check the lens on another camera?

My location is in France nearby Rennes. and for pentax france the repairing company is "PM2S" but onee I need their services for a flash problem :
I let my K5 and the af360fgz flash during one month for investigation , and they send them me back , whith the following diagnostic : all is ok.
but the problem was still present, I go in a photo shop close to home, in five minutes the diagnostic was : the flash is wrong, and it was true.
So for the 18-135 focus issue, I am not confident to ask for the PM2S help.

I am sure it is a lense problem : on a old K100ds it is exactly the same.

In october i will travel in Viet Nam, I am interested for the "water resist" capability of the 18-135 lense; anyway I will take with me a 21mm limited . it's the focal lense where the 18-135 focus is wrong.
Anyway , Jak thank you very much for your help.

You can't check the auto focussing of an 18-135 on a K100D as that camera isn't equipped to handle Pentax's DC (or "Direct Current") autofocus motor lenses, and that lens lacks screw drive focussing. They're not really compatible though manual focussing should be possible. The lens ought to be OK with the K-5 but a test on another compatible body might help prove the problem is with the lens and not the camera, given the camera may have other issues.
Is the flash problem just when using the 18-135? If so the camera and lens might well be fine as PM25 reported.
It would probably help if you could visit a specialist Pentax dealer or Pentax owning friend who could check each item against a known working one to identify where any problem lies.

The K100Ds (Super version) has the correct contacts for SDM/DC motors.

Well I know my old K100D wasn't compatible with SDM, but then it wasn't a DS. I'm surprised a major update like that didn't warrant a compete new version number rather than just an added S. I tried a Google search for K100DS and nothing showed up, just Pentax K100D Super. And as we know, all Pentax's are super!

Bottom line then, it seems to confirm the lens is duff.