Sigma Art 30mm f/1.4 DC (Dx)
Introduction
For a number of years Sigma has been known as a cheap, third-party alternative lens marker. While not exactly copying a name brand lens, they often didn't stray too far from the popular lens sizes. At some point in the late 2000s it seems the folks at Sigma wanted to change that stereotype and wanted to engineer their own high quality lenses that would exceed competitors and create new lens types, filling holes in available offerings from competitors (faster lenses or longer lenses than others are making). They called this new series of lenses ART lenses to denote their intended use by artisans.
The 30mm f/1.4 lens is capable of more than Sigma has let on making this a great find to (mis)use beyond its listed potential.
Marketed as a "DC" lens (Sigma's say of denoting Dx-crop and not the Nikon "Defocus Control" as seen on their amazing portrait lenses) it works great as advertised on a smaller sensor. But something happens when you put this lens onto a full-frame camera: the image seems to cover the sensor quite well.
There is some light fall off in the corners, more than one might want, but it works - it works quite well actually. If you use it on a full-frame-sensored camera you can shoot full frame and decide how to crop later. This means you can decide how to crop, and therefore push the limits well beyond the tiny Dx sized crop.
Being f/1.4 this is a very fast lens to have in your arsenal and I do recommend owning one if you get a chance at an affordable copy.
Specifications
The lens is setup with 9 elements in 8 groups.
Maximum Aperture: f/1.4
Minimum Aperture: f/16
The diaphragm is 9-bladed with rounded blades, producing high quality bokeh. Points of light are nice, well-controlled circles that blend smoothly into the background.
Auto focus with simple manual override at any time you want.
Construction
Made out of polycarbonate this lens has a cheap, plastic feel to it.
The focus ring is covered in a rubber grip that is more comfortable than many other lenses I've used.
The lens hood is a full circle, not a pedal style. The hood does not stick out too far making it easy to access the lens cap. I leave my lens hood on the lens all of the time, pointed out.
Performance
Keeping in mind I enjoy (mis)using this lens as a full frame, FX lens. This is contray to the crop-factor Dx size and how Sigma intended this lens to be used.
When used on a Dx camera the 30mm behaves like a 45mm lens, a quite normal lens indeed. Great for portraits and other uses for which we buy a "normal" lens like this. On Fx things get wider and more fun.
The coating in this lens is nice, nicer than many Nikkors, nearly as good as a Voigtlander, the kind of company I thought Sigma was going to go after with their ART series of lenses. However, a prime lens that is this fast and has accurate auto focus should be twice as expensive as this Sigma has set the MSRP. This kind of makes it feel like a cheap, third-party alternative again.
Though a good cheap, if that makes sense, given the f/1.4 performance, optical sharpness, and great colors. The feel of the lens is cheap, with its plasticy feel and the price is cheap, but betraying all of that is the high quality optics.
Alternatives
The 30mm offering straddles the 28mm lenses and the 35mm lenses, each being quite common but not as fast as this lens (and few having as good of optics). It seems Sigma targeting something no one else was doing, the fast 30mm prime.
Examples
Following are some sample photos to demonstrate the power of this type of lens and some general uses which will likely yield good results. If you shoot things like these, then this lens may be a good one to think about adding to your camera bag.
Check out more photos I have shot with this lens in my Flickr Album.