Nikkor 55-200 focusing problem

[james_tigerwoods]

Yesterday I was at a village fete and the Dakota flew over - lovely aircraft it is - I was trying to shoot it but the lens, for some reason wouldn't focus properly.

If it had focused all the way "out" it wouldn't bring itself back - I had to manually focus it and then it would do the short focus just fine.

I check the AF-x settings, that the camera (Nikon D3100) was working fine (the 18-70 had been fine) and all seemed well - I can replicate this at will and am stumped. This is a new problem and the lens has previously been fine.

It is still sharp (for the 55-200 AF-S VR) but it's just this that I'm stumped about.

Is it a lens problem or could it be a camera setting problem?

Thanks,

JTW

[ManFromDelmonte]

Even if you point the lens at something largely featureless (like a blue sky), I thought the lens would likely fail to find focus but it would at least do a full scan out to infinity and back to the closest distance.

Are you saying it focuses out to infinity (and beyond) and then stops? It does sound like something is wrong.

[andy-xr]

If it doesnt move at all when you try to focus it's either set to manual focus on the lens or you've set something up different. That lens is a bit of a POS in focus terms anyway, probably not helped by not having much contrast points to focus against

[james_tigerwoods]

It's the lens - it sounds a bit "gravelly" when focusing so I think it's on its way out

It'll focus fine up to about 180mm, but when fully extended, it's not very happy.

I don't use it a huge amount anyway but it's always been a nice to have - the 35mm and 18-70 are the two lenses I really "need"

[LongQ]

james_tigerwoods said:

It's the lens - it sounds a bit "gravelly" when focusing so I think it's on its way out

It'll focus fine up to about 180mm, but when fully extended, it's not very happy.

I don't use it a huge amount anyway but it's always been a nice to have - the 35mm and 18-70 are the two lenses I really "need"

I have a Canon lens that could be described in much the same way.

One of the problems at the longer end may be that the f-rating (f6.3 in my case) is taking a typical body to the limits of its focusing ability (f5.6 on the centre point sensitivity). So it can just about focus well given a decent chance (good light, something with a well defined and differentiated boundary to focus on) but is somewhat less than average in normal hand held, shooting on the fly stuff. And usually dreadful with anything that is moving.

Add in the potential for something being a little "broken" in the mechanism and erratic results are pretty much guaranteed.