06-07-2012, 12:51 PM
(This post was last modified: 06-07-2012, 12:58 PM by Brightcolours.)
[quote name='photonius' timestamp='1339071654' post='18739']
As far as I know, USM seems to be very fast, faster than micromotors. Why would it not be fast enough for contrast detect, what else would be faster than USM?
[/quote]
USM does not react fast enough for the small steps contrast detect needs. It is not about speed but the way the motors are being used. USM is fine for PD AF use, where the motor does not have to stop moving for focus check.
As I said, this is the reason Olympus uses MSC motors in the contrast AF based MFT lenses, and not the SWD motors (USM clones) they used in PD AF DSLRs.
http://www.olympus.com.au/Learn---Explor...ology.aspx
As far as I know, USM seems to be very fast, faster than micromotors. Why would it not be fast enough for contrast detect, what else would be faster than USM?
[/quote]
USM does not react fast enough for the small steps contrast detect needs. It is not about speed but the way the motors are being used. USM is fine for PD AF use, where the motor does not have to stop moving for focus check.
As I said, this is the reason Olympus uses MSC motors in the contrast AF based MFT lenses, and not the SWD motors (USM clones) they used in PD AF DSLRs.
http://www.olympus.com.au/Learn---Explor...ology.aspx