Lab

Digital Cameras

When you get your new digital camera out of the box on Christmas day, you don't want to have to spend the whole morning reading the manual and the whole afternoon fiddling with its settings before you can take your first shot. You just want to be able to point, click and snap everyone else opening their presents without the hassle of mucking around with menus.

By the time you come to take next year's holiday snaps, however, you'll have mastered all the basics. At this point, a camera that doesn't provide enough presets, shooting modes and manual settings to give you control over how your photographs turn out can quickly become boring and frustrating. That's why we've tested six cameras for under £200 that don't just offer point-and-shoot convenience, they give you a good degree of creative control too.

How Digital

Cameras Work

A digital camera works in much the same way as film cameras. Light is focused through a lens, or series of separate lenses, onto a light-sensitive surface in order to create an image. Instead of a chemical film, however, the lens focuses light onto an electrical sensor, usually a charge-coupled device, or CCD.

A CCD is a chip made up of thousands of light-sensitive cells. When light strikes the chip, each cell registers the intensity of the light that falls on it. The more cells in your CCD, the greater the level of detail your camera can capture. This figure is measured in millions of pixels - megapixels - and is referred to as the camera's resolution.

By combining the readings of all the cells in the CCD, the camera builds up a picture of an entire scene, with all the various intensities of light and shadow. If this were all the information that the camera recorded, however, then it would only be able to take black and white pictures. To add colour to the image, a succession of coloured filters - red, blue and green - are passed in front of each 'cell' in the CCD. By measuring the intensity of each of these colours, the camera can calculate the actual colour of any point in a scene.

For any of this information to be useful to a computer or a printer, however, it needs to be converted from analogue values to the digital binary code that computers understand. This is done by something called an analogue-to-digital converter chip.

Once all the information needed to create a picture has been recorded, the camera applies some form of compression, removing information that isn't required. This is necessary, otherwise each photo would be huge and only a few photos would fit even on a large expensive memory card. The resulting digital image file is then saved to the camera's memory card, usually as a JPEG file.

Like a film camera, digital cameras also need to be able to control how much light hits the light sensor and how quickly. This can be done by changing the size of the camera's aperture, the hole through which light passes to hit the CCD; and by changing its shutter speed, the length of time for which the shutter stays open, allowing light to pass. Some cameras automate both functions, while others allow you at least some manual control.

Even if they don't give you full manual control, many cameras at least have a number of preset shooting modes, for instance night modes, portrait modes and indoor modes, which customise these and other settings for particular environments.

What To Look For

The first thing to keep in mind when choosing a digital camera is not to believe the megapixel hype. The number of pixels in a camera's light sensor is only one factor determining the level of detail a camera can resolve. It's important, but it's not the be-all and end-all.

A modern camera shouldn't have less than a 5-megapixel CCD, but it doesn't automatically mean that a 6-megapixel camera will take better pictures than a 5-megapixel one. Lots of other factors also affect image quality. The condition of the lens, the standard of the circuitry, the compression settings and the quality of the camera's drivers are all as important as the megapixel count.

Compression settings, in particular, can greatly affect image quality. Some cheap digital cameras greatly compress images when they're saved to memory. As a result of so much information being discarded, areas of near uniform or very similar colour and texture end up looking blotchy, pixellated and speckled.

Unfortunately, it's very difficult to tell anything useful about image quality and many of the factors that determine it, just by looking at the camera's specifications. That's why comparative tests like this are so important - they're the only way to really find out which cameras produce the best pictures.

When considering picture quality, it's also important to take into account what kind of zoom the camera has. Some cameras quote very high zoom ratings by multiplying digital and optical zoom values. Digital zoom, however, is of little practical use - it simply crops in on a portion of the image, just as you would with an image-editing program. It doesn't add any extra detail to the magnified image. Only the optical zoom is worth bothering about.

For a compact digital camera, one of the most important things to look for is ease of use. If you're at a party or on the beach, you don't want to have to fiddle with lots of settings to get a good picture, you just want to be able to point and shoot. Your camera should have an automatic mode that produces good-quality shots.

In some circumstances, however, you may want more control than the automatic mode offers - if you're taking a portrait, for instance, or composing a landscape shot of a favourite scene. In these cases, you'll need to be able to switch automatic mode off.

Your camera should offer you at least some manual control over settings like aperture, shutter speed, white balance - setting colour values by correctly locating white within a picture - and so on. You should also have various preset modes for different environments or projects including indoor, portrait and landscape shots.

Some digital cameras also offer a number of ISO settings. In film cameras, the ISO of the film denotes its sensitivity to light. A film with a high ISO rating is more sensitive to light and therefore better to use in low-light conditions. The ISO settings on a digital camera work in the same way: the higher the ISO setting the greater the sensitivity to light - but there is a catch. You can't really make a CCD chip more sensitive to light than it is. All you can do is amplify the gain of the chip - that is increase the value of its output signal as a ratio of the input signal. This doesn't just increase the values produced by the light which falls on the CCD, it also increases the value of any digital noise or interference, introducing distortion into your pictures. If a digital camera has ISO speed settings they need to be very well implemented, otherwise they do more harm than good.

As well as image quality and ease of use you should also check the time a camera takes to recharge between shots. There's nothing more frustrating than continually missing actions shots because your CCD or memory card isn't ready. A good camera should also be robust enough to stand up to a few knocks and bumps.

Buying Decisions

There are two clear winners in this group test. The FinePix F10 is highly responsive, which is great for rapid shots, gives you detailed control over most - though not all - of the important settings and has a decent 6.2x optical zoom lens. It also captures lots of detail with its high resolution CCD. Compared the Canon PowerShot A610, however, the Fuji's pictures weren't quite as good.

Although bulky, the PowerShot took excellent pictures both indoors and outdoors, and in all our tests. The only test in which is fell behind a little was when we took pictures in low light conditions - even here, though, it's results were nothing to complain about. The PowerShot also had an impressive selection of presets and manual controls, allowing you to take much greater creative control when you want to. Taken together, all these things make the Canon the clear winner in this group test and an equally clear Best Buy.