Severe Problem with my lens's autofocus just began!

[joshua_efron]

 

 

<p >Hi everybody.<br>

I've just started having problems with my Promaster-branded Tamron-Made 17-50 2.8 on my D300. It's doing what I will call "focus rocking" - it will overshoot focus, overshoot the correction, overshoot the reverse correction again, and then finally lock on. The number of misses varies, but it often about four before the lens is finally in focus. And sometimes it's still off.<br>

I've tried the different focus modes, different focal lengths, different exposure modes, different apertures, different shutter speeds. I've remounted the lens with the battery off, I've changed batteries, I've tried a freshly charged batteries. I've shot under different lighting conditions, including outside in good sunlight.<br>

I've tried testing the lens, putting another (working) lens on, and putting the Tamron back on the camera.<br>

The contacts look clean (I don't have proper cleaning tools but used the oft-repeated gentle pencil eraser maneuver), and the lens, to my knowledge, was never dropped. It seems to have just started doing this without provocation.<br>

It's been a couple of weeks since this started. As I said, I can't remember any cause for this - drops, submergings, anything.</p>

<p >Any ideas? I really appreciate the help!</p>

 

 

[walterh]

<p>Sounds like you need to send it in for service.</p>

[CvhKaar]

<p>Just an idea : did you try other lenses on this cam, and this lens on another cam. so that you know wether its the lens, the cam or the combination ?</p>

[kohanmike]

<p>Until two days ago my 2 month old 17-50 VC seemed to be working great, sharp and fast, but looking at the results of my last job shooting a philharmonic concert in the lobby of the Dorothy Chandler Pavilion, the lens seems to be having back focus problems, only at times, not always. I'm doing a portrait job on Monday and will be more observant of it. I hope I'm not a victim of the notorious quality control issues and have to send it to Tamron.</p>

[jorish]

<p>You might also find useable info in Thom Hogan's <a href="http://bythom.com/autofocus.htm">'Autofocus Troubleshooting' article</a>.</p>

[joshua_efron]

<p>None of my other lenses are exhibiting the same problem on my D300, and the faulty lens -is- exhibiting the same problem on my D70.</p>

[CvhKaar]

<p>Ok Joshua, then your lens obviously needs "servicing"..<br>

I do not know how old that lens actually is, but if you bought it less than a year ago , it may be still on warranty ...<br>

BTW, even the gentelest erasers are no good for gold contacts, they are just to abrasive... I know that sometimes technicians are thougt to use erasers, but those are, or should be, special pieces of latex rubber impregnated with a cleaning agent for contacts of <strong>printed cirquit bords </strong>.<br>

If you want to clean those contacts its saver to use a feld tip with a small drop of pure alcohol ( so no boose... :-) ). This removes an eventual layer of "grease" of without damaging the contacts, whereas an eraser just moves the grease around because it gets greasy itself and damageing the thin gold layer of the contacts....</p>

[eric_arnold]

<p>just wondering if promaster has the same warranty as tamron?</p>

[CvhKaar]

<p>Eric , is this what your looking for : <a href="http://www.promaster.com/support/repairs.asp">http://www.promaster.com/support/repairs.asp</a></p>

[eric_arnold]

<p>thanks CPM. that warranty is even better than tamron's, so the OP should be covered. i dont own any Promaster lenses btw, but i do have the 17-50 tammy.</p>

[wentbackward]

<p>Do you have a UV filter? Nikon Hong Kong advised me to remove it when my D3 was giving lots of trouble. I had just bought it and upgraded from a D300 which had minor problems with hunting AF.</p>