55-300 repair

After a past topic on the forum with regard to a focusing issue I have with the lens, I was kindly suggested by a fellow pentaxian to send the lens to AM Technical Services in Middlesex. Basically the lens is very soft from pretty much 100mm through to 300mm. Problem now is the technician cant find where the defect is with the lens and needs to get in contact with pentax to find out if they are aware of any problems with past lenses. Any of you guys got any ideas out there what the problem might be?

https://www.pentaxuser.com/images/comment_pictures/9164/9164_1369587894.jpg

Are you using any filter on the lens? If so, remove it and try it again. The 55-300 does not like filters of any kind.

Secondly, is the lens calibrated to the camera for AF? If not, it should be and this could be the problem. My 55-300 is fantastic, but almost got binned when I first owned it. The focus accuracy with my first K-x was abysmal, then I tried it on a different camera and it was transformed. I wouldn't assume the lens is at fault until you have eradicated all other possibilities.

Regards
David

+1 with David on this, my 55-300 is astonishingly good for what is really a cheapish kit zoom lens. The AF is, on mine at least, pretty awful though

I assume you have tried focusing the lens manually - that would decide whether or not the lens was at fault?

Roger.

there are a couple of lens elements positioned on shims. Dunno the effect of getting one that's been badly done in the factory.

Tried taking the uv off. Doesn't change anything. Manual focus is so hard to pinpoint as the soft focusing is only visible on the computer. Tried calibrating, but had no luck. Ay other thoughts greatly appreciated

Looking at the sample image I'd say you have either been very careless with your focus test or, if the target is actually flat, there is something really, really wrong with that lens.

If your lens technician can't find the fault sending it to Pentax for fettling seems the next step.

Already sent it to Pentax (Foya) in France through a local camera retailer and without great description I was told the lens would cost about 200 pound to get fixed. Not really worth it considering you can by a new one for that price

Mind you, the lens did work perfectly prior to a trip to Argentina last year some something is surely broken or jolted I'd say

I would be tempted to buy a new one, after reading more of this thread and seeing your sample image. The DA L version can be bought new for well under £200, this is the one I have and it is superb. I've never felt the need for 'quick shift' and the plastic lens mount is not an issue for me. If you get a good copy of this lens you will be impressed by its performance.

Regards
David