A lens to consider
This lens is a digital-specific lens designed to provide a normal focal length with a wide maximum aperture on a DSLR with a crop factor. It is not designed to work on a full-frame or film camera. It is the only lens on the market manufactured specifically for this purpose. Other similar lenses are designed as wide-angle lenses that happen to give a normal (~48mm) length on a APS-C size sensor camera.
For what it is, this lens is an expensive one, but feels well-made, if not rock-solid. Before buying, make sure you will be making good use of the large maximum aperture. If most of your work is not in low light, another lens might be a better, more economical choice (Sigma makes a 24mm and a 28mm which are f/1.8). In low light, the lens is able to focus decently well, without flopping around. The focusing is internal, pretty fast, and almost silent. Additionally, the lens supports full-time manual focusing adjustment, which means that once the lens has autofocused, you can still use the focus ring to adjust focus without fear of stripping the AF gears. I don't end up using it, but it's nice to have and know that if I bump the focus ring, I'm not shredding the mechanism.
Macro-wise, there's not a lot to offer from this lens. Sigma makes similar, slightly wider lenses at f/1.8 that have a macro function, but I've never tried them. Sharpness-wise, it's decent but softish when wide open or close to wide open in low light, but I've gotten lucky and gotten razor sharp focus in good light at f/2.0, which could make this lens a candidate for portraiture.
Bottom line: if your favorite film lens was your 50mm f/1.4, this is a natural choice. If your favorite lens was one of the toy Canon 50mm f/1.4 Mark II's this lens feels like much more of a tool and precision instrument; and it costs as much as 5 of those. If you work in low light and need a wider focal length than 50mm and a maximum aperture faster than f/1.8, this is a good lens for you, too. If you use a fullframe camera, don't even bother. Sigma designates this lens as a specialty lens, which I find ironic because what this lens is equivalent to the golden standard in both art and much of documentary photography for years. I guess people are shifting in the direction of zooms with image stabilization instead of more glass and faster apertures, but for those of us in the older school, this may be a good choice.Read full review
