Nikon 70-200 2.8 focus off?

[KenRC51]

I just bought a like new 70-200 2.8 VR1 off craigslist. The lens is perfect, no scuff, no rubber wear from over use, no scratch on lens. Its almost like a brand new lens.

The lens is very sharp and focus really fast but I find that when I'm shooting a moving object like my dog the lens would not focus on the dog instead it would get the ground or grass right below or on the side of the dog. When I look through the eyepiece to take the shot the dog looks really clear.

This only happens when the dog is running. Still or minor movement like walking would be crystal clear and focus right on spot.

Shots were shot in Aperture priority (2.8 mostly), iso 400, during later evening shutter speed was around 1/500 to 1/1000, af mode was AF-C, Focus mode was where I can chose a spot focus, and 3d tracking.

Is there a test I can do to see if the lens is focusing off? I'm pretty sure the its not from user error. I am not a pro but I never had this problem with my 24-70 2.8

[kirbinster]

I am almost certain it is not the lens. Your depth of field at f/2.8 is going to be very shallow on a long lens, which may be one issue. The other issue is how you have the camera set up to use focus tracking. Many times it will pick the wrong item. I would first make sure that the lens works by chosing single point focus and make sure your shots are sharp. If so the lens is fine. Then work on your tracking settings in the camera.

[KenRC51]

Originally Posted by kirbinster

I am almost certain it is not the lens. Your depth of field at f/2.8 is going to be very shallow on a long lens, which may be one issue. The other issue is how you have the camera set up to use focus tracking. Many times it will pick the wrong item. I would first make sure that the lens works by chosing single point focus and make sure your shots are sharp. If so the lens is fine. Then work on your tracking settings in the camera.

I was using dynamic area & 3d tracking with single point focus. You right it might be the DOF. I haven't had much time to play with it but I will do this weekend.

[OsmosisStudios]

Originally Posted by KenRC51

I was using dynamic area & 3d tracking with single point focus. You right it might be the DOF. I haven't had much time to play with it but I will do this weekend.

Even so, it might not be able to keep up with the dog's movement.

[sk66]

I use C and Dynamic mode for most moving subjects. I seldom use 3d mode however as it requires distinctive color differentiation from the background (and some consistency to it).
I don't think the D90 has a focus delay setting (my D3 does). If it does, this tells the camera how long to wait before refocusing should the primary sensor fall on a new "subject". I usually have this delay set to "long".
Also, in C mode the camera is probably set to "release + focus" (the default). This means the camera will take a picture without getting focus first. You can change this setting to "focus" and then the camera will not fire unless focus is attained. I'd try changing that setting first.

[KenRC51]

Originally Posted by sk66

I use C and Dynamic mode for most moving subjects. I seldom use 3d mode however as it requires distinctive color differentiation from the background (and some consistency to it).
I don't think the D90 has a focus delay setting (my D3 does). If it does, this tells the camera how long to wait before refocusing should the primary sensor fall on a new "subject". I usually have this delay set to "long".
Also, in C mode the camera is probably set to "release + focus" (the default). This means the camera will take a picture without getting focus first. You can change this setting to "focus" and then the camera will not fire unless focus is attained. I'd try changing that setting first.

I always shoot in AF-C mode and never had a problem, rarely miss focus with my 24-70 on fast moving subject. I will have to try in single focus mode to see if it works better but then that defeats the purpose of using burst mode and shooting fast moving subject.

Other than the focusing with fast moving subject this lens is freaken crazy, I get better bokeh and crispier shots than my 24-70. I think I found my new portrait lens.

[sk66]

I'm not suggesting using it in Single servo mode, just change the C mode to "focus" instead of "release+focus".

[KenRC51]

If my lens focus perfectly on non moving or slow moving subject then does that mean there are no focusing issues with my lens? I'm still having focusing issues with fast moving subject.

I have finals this week but once it's over I will post some example photos so you guys know what I'm taking about.

[kirbinster]

If it focuses perfectly on still objects then there is nothing wrong with the lens, it is either the camera, or the operator

[sk66]

Originally Posted by kirbinster

If it focuses perfectly on still objects then there is nothing wrong with the lens, it is either the camera, or the operator

Probably, but not necessarily.

You could have a SWM that is slow/dodgy. I had a focus motor go out in one of my lenses and it initially showed as slow/missed focus, then it became intermittent operation, then it just died. (this was on a sigma lens btw)