After the telephoto zoom lens, the most prefered and useful accessory for a DSLR is a super-wide-angle lens.
Majority of kit lenses bundled with the DSLRs offer a widest focal length of 28mm equivalent, and 24mm in some cases. This is the most basic lens setup you'll see on most cameras but the the wide angle of view they provide is not enough.
When you observe closely, the 28mm lens does not suffice when it comes to photographing large buildings, or while taking group shots across a narrow street. Also, it sometimes gets difficult to fit everything in frame while 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, 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 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.