Minimum focus is a constant 0.24m over the zoom range, and the round diaphragm provides exquisite bokey (blur effects). The internal focusing system with its ring-type USM is quick and quiet, while the full-time manual focus enables manual focusing even in autofocus mode. The lens mechanism is designed to ensure that it fits only EOS DIGITAL SLR cameras designed to take EF-S lenses, and it is equipped with a special attachment indicator and protective rubber mount ring to prevent mistaken attempts to attach it to other EOS SLR cameras, and to prevent damage to the camera body. 

NOTE: Can only be used with digital SLR cameras that support EF-S lenses. 
 

Compatible with EOS Digital SLR cameras: EOS 50D, EOS 40D, EOS 30D, EOS 20D, EOS 20Da, EOS Kiss X2/DIGITAL REBEL XSi/450D, EOS Kiss F/DIGITAL REBEL XS/1000D, EOS Kiss Digital X/DIGITAL REBEL XTi/400D DIGITAL, EOS Kiss Digital N/DIGITAL REBEL Xt/350D DIGITAL, EOS Kiss Digital/DIGITAL REBEL/300D DIGITAL (as of August 2008)
 
 
 
 
 
Filter size: 77mm
 
 
Max aperture: f/3.5-4.5
 
 
With ring USM motor