Lab

Ultra-zoom cameras

A digital camera's zoom is its most important feature. The 3x zoom found in most digital cameras provides a blinkered view of the world, and, unless your camera came bundled with a jet pack, you'll struggle to compose truly great photos with such a limited zoom range.

A larger zoom is often all it takes to turn a casual snapper into a creative photographer. It gives you much broader scope to explore interesting compositions within a view, creating symmetries and juxtapositions within the frame. You don't have to have creative aspirations to appreciate a big zoom, though. You'll suddenly find that you're able to capture distant subjects with as much detail as the naked eye can see. You'll also be able to photograph people while keeping your distance, which invariably results in more natural, relaxed portraits.

For a given size of sensor, the magnification achieved by a zoom lens is dictated by the distance between the centre of the lens and the CCD. This distance is called the focal length. When we talk about a 3x or 10x zoom, this value is the ratio between the shortest and longest focal lengths a lens is capable of. Bigger is better, but there's more to a zoom's specifications than this simple figure. Zoom ranges are commonly quoted in the format 35-350mm. These are the equivalent focal lengths that would produce the same results in a 35mm film camera. In a digital camera they're really much shorter because the charge-coupled device (CCD) is smaller than 35mm film, so the entire lens mechanism can be miniaturised accordingly. However, focal lengths of digital cameras are quoted as 35mm-equivalent values, as this helps us compare like with like, regardless of the size of the CCD.

To find out more about a camera's zoom, you also need to look at its focal length range. A fairly typical 3x zoom for a compact digital camera is 35-105mm, but entry-level digital SLRs tend to come with 18-55mm lenses. This gives a wide-angle view that's more similar to the panoramic view humans can see, but the downside is that everything is smaller. At the opposite end of the scale, the ultra-zoom cameras on test here have ranges in the region of 38-380mm, which means their wide-angle view is similar to the average compact camera, but they magnify up to four times as much at their extreme telephoto setting. The two exceptions are the FujiFilm cameras, which range from 28-300mm. This gives a slightly less enlarged maximum setting but enables wider-angle photography at the opposite end.

Zoom ranges are all about ratios, so the difference between a 28mm and a 35mm focal length is just as acute as the difference between 300mm and 375mm.

Adding more pixels to your CCD is also beneficial for photographing far-off subjects. However, a 10 per cent increase in focal length gives you 10 per cent more detail both vertically and horizontally. This is much more beneficial than 10 per cent more pixels, which gives you a resolution just under 5 per cent higher on each axis. In short, a big zoom is good news.

FIT THE STABILISERS

The downside of all this magnification is that any wobbles are magnified, too. It's a generally accepted rule that you can achieve a sharp image without blur from camera shake if the shutter speed is one divided by the focal length. This means that, with a 35mm focal length, you can shoot at around 1/35 seconds and keep things sharp, which is a reasonably practical figure for shooting in bright artificial lighting. However, increase the focal length to 400mm and you need a 1/400-second shutter speed, which is normally practical only in bright sunlight.

The simplest solution to this problem is to use a tripod, which banishes shakes altogether. The cheapest is to go into a Zen-like meditative state, eliminating any movement by sheer will-power, but the best solution is to choose a camera with optical image stabilisation. These systems use tiny gyroscopic sensors that detect movement as the picture is taken, and adjust either the lens or the CCD position to counteract it. However, the results can be hit and miss, as they can compensate by only a small amount. If you go beyond these limitations, the picture will probably be as blurry as if you didn't use stabilisation at all.

The second-best solution is to use a high ISO setting, which increases the CCD's sensitivity and thus allows for faster shutter speeds. Double the ISO speed and you can double the shutter speed, although the downside is that you'll also be doubling the amount of image noise.

Unlike image stabilisation, this reduces only the amount of blur rather than attempting to counteract it, so it usually needs to be coupled with your best meditative skills when shooting at high telephoto settings. However, high ISO speeds will reduce blur caused by a moving subject as well as a moving photographer, which can be useful.

SNAP DECISION

Armed with this knowledge, you should have a good idea of what makes a good ultra-zoom camera. However, it's also vital that the camera you choose fits all the usual criteria, too: high image quality, not just in well-lit conditions but also when shooting in low and artificial light or using the flash. Creating a large zoom range puts bigger challenges on the lens design, so these cameras are more susceptible to inconsistent focus, whether in the corners of images at wide-angle settings or because the auto-focus gets confused at high telephoto settings.

Battery life, performance and ergonomics must be considered, too. Because many of these cameras appeal more to enthusiasts, they should include advanced photographic options, along with accessible controls and clear visual feedback for adjusting them.

We have reviewed all the ultra-zoom digital cameras currently available, with only the odd exception that we've already covered in previous reviews. We're delighted to report that we found three fantastic cameras for three different sorts of user, so read on to discover the one that's perfect for you.