Sigma 105 mm f/2.8 EX DG OS HSM Macro
10. Autofocus
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The autorocus works silently – after all we deal here with an ultrasonic mechanism. It speed is not impressing, though. Running through the whole scale takes about 1.7-1.8 seconds. When we use the focus limiter, choosing the range from 0.45 of a meter to infinity, this value decreases to about 0.8 of a second. It is not a result we would admire, especially that in this range the lens has to move the elements in a very short distance. Rival devices from Canon and Nikon have noticeably better results here.
The accuracy of the mechanism would be hard to blame because the number of misses didn’t exceed 5%. We must emphasize, though, that it was only true after the calibration of the autofocus. Before the calibration, both on the 1Ds MkIII and on the 50D, the lens showed a significant back focus. Only after setting the microcalibration parameter at –15 units you could enjoy the right focusing.
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