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
