What you are seeing is quite common, but I would not worry about it. It is rare that one focuses from an extreme (MFD or inf) in the real world. Most AF focus changes are in much smaller increments. Or put another way, one cannot expect a fast lens to come to an abrupt halt at the perfect focus point. Just too much inertia, mass and variables. In the real world, one would focus from an extreme and then refocus. So in your testing I would suggest a minimal focus *move* in between test shots. I always do the first shot from an extreme, but then ignore that shot in my review, and *de-focus* slightly between shots, just to make sure that the AF system does a complete refocus. We recommend taking at least 3 shots, with slight de-focus in between, just to make sure that the AF performance is consistent from shot to shot. There will be *some* variability, but 80% of the shots should be very close. large and consistent variability is usually indicative of a defective lens that need calibration at the factory...or too low a light level on the focus target.
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