Sigma 35mm F1.4 DG HSM "Art"

Autofocus

The Sigma 35mm F1.4 features Sigma's HSM (hypersonic motor) in-lens autofocus system.  It has no provisions for traditional screwdrive autofocus, which means that will only focus on Pentax DSLRs from 2006 and later (including the K100D Super, K10D, and all newer models).

The HSM system in this lens is both silent and fast.  As the 35mm is not designed for high-speed shooting (i.e. sports), we only evaluated its focusing performance subjectively.  We believe that the AF system in this lens does what it was designed for very well.  The autofocus locks on in fractions of a second* thanks to the short (90-degree) focus throw, and on top of that, it is virtually inaudible. 

Based on user reports on our forum, the Sigma HSM system is much more reliable than Pentax's SDM autofocus.  Furthermore, thanks to the 4-year standard Sigma warranty, you can enjoy peace-of-mind for 3 years longer than with a Pentax lens (2 years longer in Canada and Europe).

*when tested on the Pentax K-5 and K-50 DSLRs