APS-C, or crop frame DSLRs, use a reduced-size sensor, which allows manufacturers to keep the cost of the cameras lower. However, these sensors are 1.5, 1.6, or 2 times smaller than a full frame sensor (which is equivalent to a 35mm strip of film), so conventional wide-angle lenses become standard lenses.
To this end, manufacturers have started producing lenses specifically designed for APS-C cameras. These lenses are super-wide (to allow for focal length conversion), and they are designed in cheaper materials to keep costs down. Here is a list of some of the best wide-angle lenses for APS-C DSLR cameras.
The Canon EF-S 10-22mm is a fantastic lens, with hardly any distortion at all. In fact, you'll only notice slight corner distortion at 10mm.
The Canon EF-S 10-22mm lens is extremely lightweight as it's made from plastic, but the lens mount is metal. It certainly feels solid enough and, while it's lightweight, it's still quite a large lens, due to the 10mm extreme wide-angle.
It comes complete with an ultrasonic motor (USM), meaning that the lens focuses silently. Autofocus is fast as well. Altogether, this is a pretty perfect lens, and it should be all Canon APS-C users' first choice. The only downside is that the Canon EF-S 10-22 mm lens doesn't come with a lens hood, which is absolutely essential on all wide-angle lenses.
Tokina's 11-16mm offering includes lens mounts to fit Canon, Nikon, and Sony cameras. While Canon users will probably find that the Canon EF-S 10-22mm is a slightly better fit, this lens should be a serious consideration for Nikon and Sony users.
The Tokina AT-X 116 lens has a constant aperture of f2.8 through all focal lengths, which is quite a remarkable achievement in a lens of this class. However, the lens does suffer from some barrel distortion, and it is a trifle soft in the corners at f2.8. But the autofocus is fast, and images are extremely sharp at all other apertures.
This is a great piece of glass.
Tamron is another third-party lens manufacturer, and its 10-24mm lens comes in a Canon, Nikon, Sony, or Pentax mount.
It's extremely well-priced in comparison to the manufacturers' own lenses, and it is one of the few without much visible barrel distortion. It's also at its very sharpest at 10mm, a fact which will be enough to sell it to many users.
However, the Tamron 10-24 mm lens is soft in the corners at all apertures and focal lengths, so a little post-production cropping will be required. This is a good budget buy, particularly for Pentax users.
Nikon's 10-24mm is a great lens, but it has a fairly steep price tag.
Optically, it's sharp, but it's prone to quite large amounts of barrel distortion. It also feels quite flimsy in comparison to its predecessor, the Nikon 12-24mm.
The selling point of the Nikon 10-24 mm lens really is the sharpness. It's sharp through all apertures and focal lengths with only the tiniest softness is the far corners at 10mm at f3.5. Even this disappears if you stop down. If you have the money and use a modern Nikon DSLR, this is the lens in which to invest.