Is AF affected by smoke?

I tried to shoot a scene from a play without flash at ISO 800 on my D40X and the 55-200mm Zoom lens.The picture

did not come out very sharp.Is it because I was at the 200 mm end or because the AF was fooled by the smoke

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Looks more like motion blur to me.

If you are using NX check the FOCUS POINT. That will tell you.

Exposure was 1/15. Handheld I'm assuming. That explains it well enough.

Using a slow shutter speed is the best way to not determine anything about focus, as Tim points out.

 

However, it depends on the source of the smoke. Some kind of smoke may cause the photographer to be less than attentive to the focus point.

I wonder if there was enough to make it hunt for focus, as the lines of contrast would be harder to find. Still, 1/15th of a second at 200mm is asking a LOT ! Even if it was a VR lens, that's a tall order.

You should have been sitting in the non-smoking area!

Well, when my 70-210 unexpectedely broke at a graduation, i was forced to use my co-workers 55-200(like the one in question) and found that it was very soft. Luckely, the parents were so glazed over by seeing "little johnny" in a cap and gown, that there were no complaints.