The Samyang 12mm F2.8 ED AS NC Fish-eye ($599) is one of the widest lenses you'll find that works with a full-frame camera, but despite this fact—as well as its f/2.8 aperture—it's quite light and compact. The manual focus lens covers a 180-degree diagonal field of view with curved fisheye distortion, and it delivers a look that can be striking when used effectively. It doesn't distort images as much as the Lensbaby Circular Fisheye, and is a solid choice for shooters seeking a unique fisheye look.

The 12mm F2.8 lens covers a full-frame image sensor, and is available for a number of different camera systems. It can be used with Canon, Four Thirds, Nikon, Pentax, and Sony SLRs, as well as mirrorless systems including Canon M, Fujifilm X, Micro Four Thirds, Samsung NX, and Sony E. When you pair the lens with a camera that has an image sensor that's smaller than full-frame, its field of view will be narrowed. In addition to the Samyang brand name, the lens is sold under the Rokinon banner.

It's not a big lens; the SLR version measures just 2.8 by 3 inches (HD) and weighs in at 17.8 ounces. Lenses for mirrorless systems are a bit longer, as the distance between the front element and the image sensor has to match that of an SLR. The lens has a physical aperture ring to adjust the f-stop, with half-stop detents and full-stop markings from f/2.8 down to f/22. It's not coupled; most modern lenses keep the iris wide open when focusing, even when the f-stop is set to a narrower value, to keep the viewfinder bright. If you stop the Samyang 12mm down the viewfinder will appear dimmer.

The manual focus ring occupies most of the barrel. It's covered in rubber and moves with smooth, even action. The lens can focus as close at 7.9 inches, and there's a printed distance scale as well as a depth of field scale with markings from f/2.8 through f/8. Manual focus is pretty easy with a lens this wide—the depth of field is forgiving when stopped down, and if your subject is more than 3 feet away, the lens can simply be set to infinity to lock focus. The front lens element is quite big, and curved—filters can't be used with the lens. A hood is built into to the barrel, and a lens cap is included for protection during storage and transport.

We normally test lens sharpness using Imatest, but our charts aren't effective for fisheye lenses. I paired the 12mm F2.8 with the Nikon D810 in the field, and was quite happy with the detail it was able to pick up in landscape shots. If you zoom in on a pixel-level, you can see some purple color fringing in high contrast areas along the periphery of the frame, but it's easy enough to remove using software and is really quite minor.

Distortion is also something that we normally test lenses for—but a fisheye lens is designed to have quite a bit of barrel distortion. If you want to minimize it and use the 12mm as an ultra-wide lens you can do so with a combination of technique and software corrections. If you're shooting a landscape, try and keep the camera level with the horizon at the center of the frame and you'll minimize the effect, as you can see in the shot below. You can go a bit further and apply distortion correction in Lightroom (none of the sample images in this review have correction applied), but that will narrow the field of view a bit.

A fisheye lens can be a powerful creative tool when used effectively. The Samyang 12mm F2.8 ED AS NC Fish-eye isn't as extreme in its look as a circular fisheye like the one offered by Lensbaby, but there's no mistaking the curved, distorted look that it delivers. It gets more extreme when focusing close on a subject, or when framing your subject toward the edges of the frame. Conversely, you can minimize the look with technique and software to make the lens double as a more traditional ultra-wide angle. Given its field of view, aperture, and the sharp results it delivers, the lens is a solid choice. Some photographers may be turned off by the lack of autofocus, but it's really quite easy to nail focus, especially if you stop down to f/4 or f/5.6. So if you're looking to expand your horizons and add an ultra-wide lens to your kit without breaking the bank, or going for the extreme look of a circular fisheye, put this lens at the top of your list.