Sigma lenses: What's the difference?

[Seekwence]

What are the noticeable differences between the Sigma 24-70mm f/2.8 Macro (~$450) and the Sigma 24-70mm f/2.8 HSM ($850)?

 

[el_shorty]

The difference between the lenses is that the more expensive one has IF and HSM.

From the Sigma Website

IF - Inner Focus
To ensure stability in focusing, this lens moves the inner lens group or groups without changing the lens’ physical length.

HSM - Hyper-Sonic Motor
This lens uses a motor driven by ultrasonic waves to provide a quiet, highspeed AF.

 

[jjparson]

I have the non HSM. For a camera with a motor I think the cheaper model is a good price for the lens. I have really enjoyed the lens and have been able to get some great shots with it. Let me know if you want more details.