The digital revolution brought many good things, along with a few bad ones. The vast majority of DSLRs sold today have a sensor which is smaller than the full Leica format, which is 36 x 24 mm. This, the so-called crop factor, is all nice and well when using telephoto lenses, as the lens seems to gain in focal length. It doesn't, of course, it's just that its apparent angle of view is narrower, because only the centre of the image is used. While this might seem like a good thing, it has pretty disastrous consequences on the wide end. That old ultrawide 20 mm lens that did such a good job at interior photography on film suddenly becomes just wide-ish, with the apparent focal length of 30 (1.5 crop factor), 32 (1.6 crop factor) or even 40 (2.0 crop factor) mm. And that's not very wide by any standards. For this reason, most entry- and mid-level cameras are sold with kit lenses covering a focal length range of 18-55 mm, which is equivalent to 28-80 mm in full Leica format.

Three ultrawide lenses. In 35 mm equivalent terms, their angle of view is equivalent to 14 mm (Olympus), 16 mm (Canon), and 18 and 19.2 mm for Tokina when mounted on Nikon and Canon bodies.

The manufacturers had to respond to a demand for wide-angle lenses. Canon made the EF-S 10-22 mm f/3.5-4.5, Nikon made the Nikkor 12-24 mm f/4 G DX, Olympus made the Zuiko Digital 7-14 f/4, Sigma made the 12-24mm f/4.5-5.6 EX ASP HSM, Tamron made the 11-18 mm f/4.5-5.6, and last, but not least, there's the Tokina AT-X PRO SD 12-24 mm f/4 IF DX. All of these lenses can capture a really wide angle even on the smaller sensors used in today's cameras. However, of all these lenses, with the exception of Sigma, project a smaller image circle, suitable only to the reduced sensor size. On full-frame cameras, they would project dark circles around images.

The protruding front element is a common feature of these lenses, making them very sensitive to incident light. This makes the lenses very prone to flare.

Ultra-wide without a huge, protruding front element? Forget about it.

Olympus Zuiko Digital, 7-14 mm. Olympus is the only camera system where all lenses are adapted to the sensor size. As the sensor dimensions are almost exactly half the Leica size, calculating effective focal lengths in 35 mm terms is very simple. A focal length of 7 mm means an effective focal length of 14 mm, while 14 mm becomes 28 mm. This makes the Zuiko Digital 7-14 equivalent to a 14-28 mm lens on a full-frame camera.

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About lens testing

You should be aware that there are many chances to really mess up a lens test. Sure, you can test - with quantitative results - image sharpness, contrast, vignetting, barrel distorsion, chromatic aberration, flare, etc. However, these results depend on focus distance, aperture, filters etc. The most important thing, however, is the method used for testing. Are we talking about field tests or lab tests, is software image analysis involved, are lighting conditions the same?

Sometimes, there are major differences between lenses. For instance, lenses with a large zoom range (7x zoom, for example) are usually worse than those with a smaller zoom range (3x zoom), while these in turn generally perform worse than prime (fixed focal length) lenses. With more people entering the DSLR world, lens tests will become more important and we'll try to bring you as many as we can.

Zuiko Digital 7-14 mm @ 7 mm. The distance from the front element to the subject was just a few centimetres, however, because of the short focal length, the depth-of-field is enormous. The same goes for perspective distortions, too. His nose isn't really that huge.

Zuiko Digital 7-14 mm @ 7 mm. This is a rectilinear wide angle lens, stretching the image at the edges.

Canon EF-S 10-22 mm @ 10 mm. Again, the perspective is immensely distorted.

Tokina DX 12-24 mm @ 12 mm. In some cases, the distortion introduced by such wide angles can be a lot of fun.

Tokina DX 12-24 mm @ 12 mm. Panoramas look great with such wide angles. Just make sure you have a few elements in the foreground to prevent the image from being too empty.

Tokina DX 12-24 mm @ 24 mm. At this focal length, distortions are hardly noticeable.

Canon EF-S 10-22 mm @ 10 mm. With extreme wide angle, the foreground is greatly exaggerated. This picture was taken at less than half a metre away from the machine, yet it appears as if it's far away.

Canon EF-S 10-22 mm @ 10 mm. Flare, the bane of all wide angle lenses. There's just no way of avoiding it. On the other hand, it's not really that disturbing in most cases.

Canon EF-S 10-22 mm @ 10 mm. These lenses are designed to produce a rectilinear image with as little barrel distortion as possible. On the other hand, they stretch the subjects close to frame edges. This makes them a lot of fun for creative effects.

Zuiko Digital 7-14 mm @ 7 mm. Despite the very short focal length, the focus distance was small enough to produce shallow depth of field.

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Canon EF-S 10-22 mm @ 10 mm. With really wide angles, ordinary scenes can appear very different, not at all comparable to the way they're captured by longer focal lengths.

Canon EF-S 10-22 mm @ 10 mm. Even with the light source outside the frame, flare is still a problem. It can be a problem sometimes.

Tokina DX 12-24 mm @ 12 mm. The lens can capture the whole room due to its very wide angle. As the main subject is sufficiently far away from the camera and in the same plane, the distortions are minimal.

Tokina DX 12-24 mm @ 12 mm. In other cases, however, these distortions can be quite disturbing, making them suitable only to demonstrate the effects of such lenses.

Tokina DX 12-24 mm @ 12 mm. You shouldn't really use such wide angles to take pictures of people, unless you know exactly what you're doing. The distortions are just too noticeable.

Canon EF-S 10-22 mm @ 10 mm. Even the tallest building can be captured at such short focal lengths.

Canon EF-S 10-22 mm @ 22 mm. (35.2 mm in 35 mm equivalent). This was taken from the same spot as the picture before. The difference in viewing angle is immense. The usually widest setting of kit lenses, 18 mm, is something of a border between wide angle and ultra wide angle.

Tokina DX 12-24 mm @ 12 mm. If the camera is not perpendicular to the building, the perspective distortions will be huge.

Tokina DX 12-24 mm @ 12 mm. In order to prevent the image from being too empty, put something in the foreground.

Zuiko Digital 7-14 mm @ 7 mm. These lenses give you access to a whole new dimension. Whether you like it or not, that's up to you and each individual image.