Lens issue

I was out today with the Nikon D300 with the AF-S 300 f/4 lens. The lens did not focus automatically, hunted a lot, and then i used it in manual mode. Camera was set at continuous low speed with dynamic autofocus. Is the lens broken or am I doing something wrong with the settings on the camera? Tried it with the D700 and the same issues occurred. All help is appreciated.

Hmmm..Ontario... are you trying to shoot snow scenes, by any chance? If so, most lenses have a tough time grabbing onto something to focus on. Try shooting something with clear horizontal and vertical lines, and see if the lens does any better.
Also, clean your contacts on the lens and camera, with an eraser (as on the end of a pencil) but be very careful not to let bits of eraser get into the camera or lens.
Let us know if this helps.
In the meantime, I'm sure others witll offer thoughts also.

Sandy

Yep, I think Sandy's onto it, Lindy. In low contrast scenes the AF will hunt like that. Frustrating. What were you shooting?

Did your other lenses have the same problem?

Thanks for everyone's thoughts. No problems using the 70-200 on either body. I missed a fabulous Northern Harrier flying closer to the car than most times. It has happened many times before and I thought it was my technique. The lens was also set at full instead of 3 meters to infinity (that was a mistake) Shot at 1/1000, iso 400, f6.7 at 300 mm

Lindy, There isn't a lot of contrast in this image, so that may indeed be the problem - PLUS your setting of "full".

Unless your view was exactly ON this fairly-distant bird (tough to achieve) , the poor AF was likely going back and forth between the bird and more distant field and struggled.
Setting to 3 metres-infinity would have helped it focus much more quickly, as you know.

Another technique to use, if you can, is to pre-focus on something close in distance to the intended image, then when you get your GOAL in sight, the lens has only small, quick adjustments to make to get good focus.

Some consolation, maybe - you would have gotten mostly the harrier's BUTT here, even if it had been in perfect focus.


Sandy

Thanks Sandy, BUTT, you should have seen the ones that got away!!

I shoot a lot of BIF shots too and most of which were on a D300 though different lenses. In my experience dynamic AF causes more problems than it solves when shooting subjects that are small in the frame and when contrast between subject and background is low. Have you tried using single point AF to see if it hunts less?

Thanks Dan, I will give that a try next time out.