First off, this is with a D7000 and 70-200 VRI, mainly near the 200mm end.

Ive noticed that my last few sets have a lot of missed focus. Consistantly about 3 feet behind the focal point in the veiw finder. Image is always crisp and clear in the view finder, but on review theyre throw aways. What confuses me is, not all of my pictures have the same problem. Some still turn out just fine. The conditions have been lighter subjects (people and young fawns to be exact) against dark green foliage, on overcast early evenings.

My first thought was not enough ambient light, but focus didnt hunt one bit and my AF typicaly still works in much darker conditions. Contrast is pretty high between the subjects and the background too.

I tested this by locking focus a few feet ahead of the subject and recomposing. Perfect images every time.

Should I use the AF calibration in the camera to correct this, or should I try something different?

This is a subject on which you will hear many opinions, but my experience with three tune-able Nikons on a pile of lenses is that most need some fine tuning. I would do that before suspecting a more general issue, however your description that it appears to be subject related is interesting.

Fine tuning does vary by zoom and distance, so you get a quadruple whammy in the 70-200. My copy (also VR1) on a D4 for example, needs AF=-3 at 200mm at middle ranges, and -20 near infinity. The good news is that it's falloff is very slow, so the actual resolving power at -3 at infinity is only down about 10%, so I can pick a happy medium. My suggestion is that to understand the problem better, fine tune against targets at your typical shooting distance, which means you can't use tools like lens align or a diagonal ruler very well, you need to shoot against the whole scale of adjustment (say in 10's first) and look at the pattern to pick the range, then further refine it. Use AF-S, single point not any tracking or auto, on a tripod, shoot several images at each distance (defocusing each time), with a delay if the D7000 will do it.

Then if you are a bit compulsive as I am, do it again at shorter distances and see how much it varies; then at 70 vs. 200; then pick a compromise.

If you find it was off, then do more shooting in real life to see if you are happier. Bear in mind real life is all that counts - focus charts and controlled tests are not the end result.

If your camera supports it, you might look at Reikan Focal. Here. I have no relation other than as a customer. It's a bit pricey but I found it worth it to get more consistent results (and if buying it you should consider the pro as if you like the product you will eventually want it). It's not well documented but you can test against ad hoc targets like a distant telephone pole with it.

Thanks for the tips! Ill get out and do some more testing to see if I can narrow it down.

I forgot to mention, I did switch from AF-A and auto tracking to AF-S with a manual focus point when I first noticed the problem. It didnt clear anything up, or help the problem.

After playing with it more, just snapping pictures of my son playing, I cant really narrow it down. Im thinkin its just somethin Im doin wrong.

Originally Posted by newb After playing with it more, just snapping pictures of my son playing, I cant really narrow it down. Im thinkin its just somethin Im doin wrong.

If you have the aperture wide open, do not use focus and recompose. Try to find a focus dot close to the area of desired prime focus and use that instead. Focus and recompose will generally result in back focus.

http://digital-photography-school.co...compose-method
http://www.visual-vacations.com/Phot...pose_sucks.htm

In really low light, when only the center focus dot finds and locks focus quickly, you may also use a loose composition with the center AF dot, and then recompose through cropping the image in post processing.

Also focus sites on the camera are often larger than the little dots in the viewfinder would have you believe-- as I discovered to my chagrin, as my camera would sometimes backfocus on the contrasty leaves and foliage, and not on the rather flat sign that I was trying for.

Originally Posted by MarkR Also focus sites on the camera are often larger than the little dots in the viewfinder would have you believe-- as I discovered to my chagrin, as my camera would sometimes backfocus on the contrasty leaves and foliage, and not on the rather flat sign that I was trying for.

Right. I describe the AF dots as "nebulous"* in nature.

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*neb·u·lous/ˈnebyələs/
Adjective:
In the form of a cloud or haze; hazy.
(of an idea) Unclear, vague, or ill-defined.

Ill go play with it some more.

Thanks for the tips!

After doing some shooting yesterday, I know I need to use the AF fine tune. Under pretty straight forward and simple conditions I just couldn't get good results. My 17-55 was out shinning the 70-200 hands down.

What confuses me is, I haven't had this problem until recently. Could dirty contact between the lens and body cause this? I don't have any reason to believe they're dirty, but I also have not cleaned them.