Quote Originally Posted by Cathathome
So by this am I right to understand that I might be attributing motion blur to DOF, and that this is really a condition of a too slow shutter? I ask because I went back and looked at the exifs for some of my shots and think that even some of the out of focus shots seem to be more evenly "sharp" when my shutter speed was closer to the (ratio?) of the focal length, e.g., 1/160sec or higher at 200mm.

Therefore, should I avoid shutter speeds less than 1/200 sec when using this lens?

Thanks,

Cath
Correct. and that is if you are shooting a still shot of someone standing. If they are moving, you need to to have an even faster. As other posters state, less than even 1/500th...depending on how fast the person is moving. If you pan, it helps.

If you want to get more into this, post some examples with the exif data.