12/31/2023 0 Comments Sigma 30mm 1.4 dc hsmGeometric distortion is moderate for a lens of this type, at 0.5% barrel. The good news is that the average CA holds more or less constant, indicating that the increase happens only around the edges. Chromatic aberration is relatively low at larger apertures but maximum CA increases gradually from f/2.8 to f/8. Shading (light falloff in the corners of the frame, more commonly known as "vignetting") is moderate (about a half a stop) wide open, and decreases in a more or less straight line until hitting a minimum of 0.13 EV at f/8 and beyond. Diffraction limiting starts to set in at about f/11, but even at f/16, the overall image is still reasonably crisp. This trend continues to f/2.8 and f/4, although the corners never get quite as sharp as the center (although they get pretty darn close at f/8. (More on this later.) Wide open, it has the softness in the corners that you'd expect, while its center sharpness is good (if not excellent.) As you stop down, more of the frame gets sharper: At f/2 there's a modest-sized sweet spot in the center of the frame, and the worst of the softness in the corners has been mitigated. That said though, it does deliver very good performance and build quality at a very affordable price: No other lens currently on the market really delivers the bang for the buck that this one does at its price point. Optically, the Sigma 30mm f/1.4 EX DC HSM performs quite well, albeit not quite up to the level we'd been expecting. (Almost a bit too much so, it's much stiffer than we're accustomed to.) In autofocus mode, it seemed middling fast on our Canon 20D test body, but definitely not as fast as some other lenses we've tested. Despite only covering an APS-C sized image area (you can't use it on a full-frame or 35mm camera), it's a hefty hunk of glass, structural plastic, and metal, and its manual focus ring has a particularly solid feel to it. (Note though, that I didn't say low light and critical shooting.) To all appearances, Sigma succeeded in their goals for it, as the lens conveys a sense of quality and solid construction. This isn't meant to be a throwaway cheapie like the plastic fantastic 50mm lenses found at the bottom of most camera company's lines, but rather a high-quality, fast lens suited for critical shooting or low light photography. All that being a long way of saying "normal". On cameras with a 1.6x crop factor (the lower end of Canon's DSLR line) it translates to a 35mm equivalent focal length of 48mm, on a 1.5x camera (Nikon, Pentax, and Sony models) it's the equivalent of a 45mm optic, and on a 4/3 camera (Olympus and Panasonic), it has the same field of view as a 60mm lens on a 35mm film camera. This is a high-quality lens (hence the "EX" in Sigma's designation) meant to provide a "normal" field of view on a sub-frame camera. It's just this consideration that prompted Sigma to develop the 30mm f/1.4 EX DC HSM lens that's the subject of this test report. With the mass move to sub-frame digital SLRs, a "normal" lens should now be something closer to 30mm, so there's a need for fast (large aperture), high-quality 30mm lenses to fill the same role as did the 50mm optics of yore. Actually though, the true definition of "normal" holds that the focal length should equal the length of the frame's diagonal, which would put "normal" at something closer to 43mm. In the 35mm film world, a "normal" focal length (that is, one which is neither wide angle nor telephoto) has always been considered to be 50mm.
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