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>

<p>I can give you a 99% "Yes" answer. I purchased an M2 extension tube for my D300 in order to mount a Pre-Ai 55mm 3.5 macro lens. The Extention tube itself is "Pre-Ai", which is normally of course a big no-no for lenses, but the tube doesn't have any of the dangerous connectors that the pre-ai lenses do.<br>

So - an M2 "non-ai" extention tube mounts safely on my D300, and there should be no difference between the D300 and D3 in this regard. Someone with a D3 will probably fill in that last 1% for you.</p>