A jaw-dropping vista will often lose more than a little something with the blinkered view of a standard zoom lens. Their shortest focal length is typically 18mm, equivalent to about 28mm on a full-frame camera, giving a field of view far narrower than you see with your eyes. Fit your DSLR with an excellent wide-angle lens and you will literally broaden your camera's horizons.
Most of us use APS-C cameras, so for this group test, we've picked eight wide-angle zoom lenses tailor-made for cameras with these small sensors. It's an important consideration - while there's no problem using telephoto zooms designed for full-frame cameras on DSLRs with APS-C sensors, it just doesn't work at the wide-angle end.
A full-frame 70-300mm lens gives you the bonus of extra reach, equivalent to about 450mm at the long end. But put a wide-angle 16-35mm full-frame lens on an APS-C camera and it will have an effective focal length of around 24-52mm, losing its wide capability.
Playing the angles, a typical 18-55mm kit zoom lens gives you a maximum field of view of about 65 degrees in the horizontal plane, or 75 degrees from corner to corner of the frame (lens manufacturers often use the diagonal plane to describe an optic's maximum field of view). Switch to a wide-angle lens that zooms out to 10mm, and those angles increase to around 98 degrees horizontally and 108 degrees diagonally. Put your eye to the viewfinder and the difference is immediately apparent.
Smaller focal lengths naturally give wider angles of view - even a couple of millimetres makes a noticeable difference. But it's not all about the minimum focal length of the lens. The focal length multiplier, or 'crop factor', of the camera also has an impact.
Nikon, Pentax and Sony DSLRs with APS-C-sized sensors have a 1.5x crop factor, giving a 10mm lens a focal length equivalent to 15mm. Canon DSLRs typically have a 1.6x crop factor, so the effective focal length of the same lens would be 16mm, not quite as wide-angled.
Olympus DSLRs' Four Thirds sensors are physically smaller, with a crop factor of 2.0x, so the effect is far more dramatic, stretching a 10mm lens to 20mm, resulting in a much narrower field of view.
Zoom ranges for wide-angle lenses tend to be around the 2x mark, as with Sigma's 10-20mm f/3.5 EX DC HSM lens. Some are smaller, such as Sony's DT 11-18mm f/4.5-5.6 optic, while others such as the Nikon AF-S DX 10-24mm f/3.5-4.5G ED and Tamron SP AF 10-24mm f/3.5-4.5 Di II have a larger zoom range of 2.4x.
In practice, however, we've found that we nearly always shoot at or near the widest-angle focal length when using a wide-angle lens, so extra zoom range isn't a massive bonus.
That said, it's useful if it reaches as far as the widest focal length of your standard zoom lens, because distortion tends to be noticeably less pronounced when using a wide-angle lens at 18mm, compared with the same zoom setting on most inexpensive kit zoom lenses.
As well as seeing a wider view, another advantage of wide-angle lenses is that you'll get a large depth of field. This is exaggerated further when using small apertures. It's great for simultaneously keeping close objects of primary interest and far-off horizons sharp in landscape images.
All but the Olympus Zuiko Digital ED 9-18mm f/4-5.6 in the group feature a focus distance scale, handy for setting the hyperfocal distance in landscape shots. This is the optimum focus distance for keeping as much in focus as possible from the foreground to the background of a scene.
For example, shooting with a Nikon camera at a focal length of 10mm and an aperture of f/11, the hyperfocal distance would be 45cm with everything from 22.5cm to infinity sharp. At f/8, the hyperfocal distance would be 64cm, with everything from 32cm to infinity sharp.
At each focal length and aperture combination, the sharpness extends from half the hyperfocal distance to infinity. For a handy depth of field and hyperfocal distance reference, try the DoF Master online calculator.
Wide-angle lenses really come into their own if you want to exaggerate perspective. You can increase the apparent size of foreground objects against dramatically receding backdrops, or make towering skyscrapers appear to lean in towards each other. The flipside is that the convergence of parallel lines makes wide-angle lenses a poor choice for accurate architectural photography.
Despite their extremely wide angles of view, all but the Sigma 8-16mm f/4.5-5.6 DC HSM lens in the group can be used throughout the entire zoom range with screw-in filters, or square filters with a screw-in adaptor.
These include landscape favourites such as ND filters, ND grads and circular polarisers. But due to the very wide field of view captured by these lenses, the amount of polarisation is likely to vary considerably across the frame.