IMHO- The real advantage of HSM (at least in the Canon and Nikon implementation) is "Full Time Manual Focussing," allowing one to touch up the fine focus after lock has been achieved without touching any switches, levers, grinding of gears, etc.... this is no small thing, after you've experienced it...
Chris L. Date: Wed, 20 Nov 2002 08:56:20 -0600 From: "Ryan K. Brooks" <[EMAIL PROTECTED]> To: [EMAIL PROTECTED] Subject: Re: New 100-300/4 and 28-70/2.8 lenses from Sigma! Message-ID: <[EMAIL PROTECTED]> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Len Paris wrote: >>It seems that apart from marketing blah blah, the only >>advantage of USM is its quietness... >> >> >>-- >>Best Regards >>Sylwek > > > I think, maybe, there could be some mechanical efficiency gained by > putting the focusing motor in the lens itself rather than in the camera > body. It could lead to slightly faster, as well as quieter, focusing. I > would need to buy a few more USM/HSM lenses to be able to say for sure, > though. > Well, it (USM) certainly seems to allow you to have AF in lenses that we don't. R
