Next to a telephoto zoom lens, a super-wide-angle optic is one of the most popular accessories for a DSLR.
Most kit lenses offer a widest focal length of 28mm equivalent, or sometimes even 24mm. This does give your camera a pretty wide angle of view, but sometimes that's not enough.
You notice it most when you're photographing large buildings or other landmarks, and when you're trying to get group shots across a narrow street, for example. It can also be difficult to 'get everything in' when you're shooting indoors.
This is where a super-wide-angle lens comes into its own – but having the wider angle of view isn't just a practical benefit. With a super-wide lens you can get much closer to your subjects without cropping them off, and this produces some brilliantly exaggerated perspectives. It goes without saying that they're perfect for landscape photography as well.
Super-wide-angle lenses can give your pictures a real sense of depth. They produce strongly converging lines that help lead your eyes into the picture and they help to create a 'story' that links your subject to its surroundings.
You can get super-wide-angle lenses made by your camera manufacturer and by third-party lens makers, but here you need to make sure you get the right lens mount for your camera before you click on the 'Buy' button. Occasionally, lenses may be sold at different prices for different camera mounts.
APS-C vs full-frame
There is something else to be aware of – it's really important that you choose super-wide-angle lenses designed for your camera's sensor size. You can use a lens designed for full frame cameras on those with smaller APS-C sensors, but you'll lose the super-wide-angle effect.
For example, on a full-frame Canon DSLR like the EOS 6D, a standard zoom or 'kit' lens will be in the range 24-70mm, so Canon's EF 17-40mm full frame lens gives a really wide angle of view.
But on a Canon with an APS-C sensor, like the EOS 760D, the kit lens will typically be in the 18-55mm range, and you'll need a 10-20mm zoom, or thereabouts, to get a super-wide angle of view.
You can fit the full frame Canon 17-40mm lens to an APS-C Canon, but you'll be using a smaller part of the image created by the lens and you'll hardly be any better off than using the regular 18-55mm kit lens.
But don't worry. We've split these lenses up into APS-C and full-frame lists so that there's no danger of buying the wrong one – and we've done this for Nikon DSLRs and lenses too.
Image stabilizers and filters
There's one more thing to explain. Super-wide-angle lenses often don't come with image stabilizers, especially those with a constant maximum aperture. This doesn't matter quite as much as it would with a regular lens since camera shake is less visible with short focal lengths – but we still mark this as a 'con'.
Second, many super-wide-angle lenses have lens hoods which are fixed permanently to the lens. This offers some protection for the large front elements, and from lens flare. But it does mean that you can't use conventional filters on the front of the lens, so, desirable as a lens hood is, we mark this down as a 'con' too.