Originally published October 2005.
WHAT YOU NEED TO KNOW:
The first high-speed "normal" lens for digital SLRs with APS-sized sensors, this 30mm f/1.4 is Sigma's first nontele lens to incorporate elements of SLD (Special Low Dispersion) glass. (SLD elements promise improved control of chromatic aberration.) The lens also has an all-glass aspheric element, in addition to a more common glass/resin hybrid aspheric.
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.
IN THE LAB:
SQF data were in the excellent range for all apertures, with slight barrel distortion (0.78%), according to our DxO Analyzer 2.0 tests -- about average for 30mm. Light falloff was gone by f/4, also average for the class. The close-focus distance was a satisfying 15.7 inches with a 1:10.2 magnification ratio.
Few lenses made for the digital arena can deliver the creamy defocused backgrounds that are possible with this f/1.4. If that look is important to your product, nature, or portrait photography, you should check it out. Of course, that f/1.4 maximum aperture also lets you shoot in a wider range of available light, sans tripod or flash. Try that with most digital-only lenses.