Your description needs correcting. The 50mm 1.4 USM lens has an ultrasonic micro motor which uses a gear assembly to drive the focus mechanism, as opposed to a ring-type USM focus that does not use gears. The micro motor USM system does not allow for full-time manual focus, and requires switching from auto focus to manual focus or damage to the gears will result. And it is also not as quiet as the ring-type USM models.
Thu, 17 May 2012 02:22:00 +0400
Thanks for pointing that out. I thought I had manual focused while in AF mode before and it felt as smooth as ring-type USM. I will try it tonight on my lens and see what happens.
Thu, 17 May 2012 02:47:37 +0400
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