Because it covers less than the full 35mm frame, you would expect this digital lens to be smaller than filmspecific 35mm f/1.4 lenses. In fact, it's considerably larger. (Pentax's 50mm f/1.4, for example, is nearly half the weight, at 0.49 vs. 0.93 pound) Why the difference? Credit Sigma's advanced, gearless ringtype HSM AF motor. Most 50mm f/1.4's either have no USM/HSM motor or utilize the micro (or "pencil") type, which uses a single gear. The Sigma's gearless ringtype is quieter (virtually silent), and allows manual touch-up focus in the AF mode, something micro motors don't. We were also impressed with this lens' AF speed.