Back focusing

[nick_the_guy]

Hey everyone, can you explain the back focusing phenomenon? I think my camera exhibits this problem. I do concert photography and so I shoot without flash or the aid of my D70 auto focus assist lamp. I use only a Tamron 28-75mm 2.8 zoom. If I focus on the performer's face, I usually get a crisp shot of the background. I can compensate sometimes by focusing on the microphone stand instead but that doesn't work if I'm shooting someone playing away from a mic stand.

You can check out my photos at www.flickr.com/photos/nicktan/show. Among the first few shots of the slideshow is a guy named El Jay. It's an example of an infocus background and out of focus performer. Frustrating!

Thanks.

Nick