need help understand tech please

[Animal]

Hi all
I'm looking at poss buying a cheapish canon zoom lens but have come across something I'm not sure what it means

for example

Canon EF 75-300mm F/4.0-5.6 USM III

I'm guessing the III is the 3rd series but what is the USM?? there are versions of this without the USM that are cheaper - so what is it?

thanks

 

[gramps]

Ultrasonic motor drive.

 

[renu]

There are plenty of info in wikipedia about USM.

 

[Animal]

brill thanks, will have a look... is it a good thing or a bad thing?

 

[ChrisJ_SLH]

USM is a good thing. Fast and quiet focusing (usually)and it usually means that Full Time Manual (FTM) focusing is possible too without switching the the lens into Manual Focus mode.

 

[Animal]

thanks everyone - will have a good look at this lens