The easiest way to determine motor type is if the lens offers Full Time
Manual Focus. The only non-Ring Type USM lens to offer FTM is the Canon
50mm f1.4 USM, which is clutched like the Pentax Quick-Shift Focus
lenses. This may not apply to the Minolta SSM lenses, although I'd
assume that they are similar to the Nikon and Canon implementations.
Note that currently the only AF-S Lenses from Nikon to not be Ring Type
are the 18-55 and 55-200 AF-S.
-Adam
keith_w wrote:
Adam Maas wrote:
The Ring-Type USM motors...
As exemplified by whom, please?
If one maker offers both, how could I identify the Ring-Type USM motors?
keith whaley
...aren't all that cheap, but they are fast and quiet (Even on a
low-end body, AF speed is similar to the best body-driven AF,
conditional on sensor capability).
The cheap ones are micro-motor USM, used in the low-end Canon USM
lenses and Nikon's 18-55 and 55-200 AF-S lenses. Cheap and not so
fast, using a small conventional motor driven by High Frequency AC,
better than the motors in non-USM Canon lenses, but not by much.
-Adam
