Lab

Buying a Webcam

Whatever Andy Warhol might have said, not everyone gets their 15 minutes of fame. But who wants to be a TV star, anyway? With one of these ingenious bits of PC trickery, you can become a legend in your own living room. Webcams are handy little cameras that plug into your PC. They let you take pictures, hold video conversations with friends on the other side of the world. They can even let you monitor your home, just as you would with a CCTV camera - and for a bit of light relief, you can use one to make your own stop-motion animation. But not all webcams are born equal, and you don't want to waste your money buying anything but the best. We pitted eight of the latest cams against each other to see which one came up trumps.

How webcams work

The basic principle of a webcam is pretty simple. Just like a normal film camera, light enters through the lens and is focused onto a square sensor inside, called a CCD ('charge-coupled device'). The CCD is just an array of thousands of minuscule light-sensitive electronic cells. Each of the cells in the CCD corresponds to one of the tiny dots that makes up a digital image, known as a 'pixel'. A few years back, many webcams were black and white, but these days they're all colour, so for every pixel in the image there are red, green and blue CCD elements. These sub-pixels record the intensity of each colour present in every pixel area. This data is then combined to create a full-colour image. A piece of circuitry called an analogue-to-digital converter (ADC) then takes the raw electrical output of the CCD and converts it into the digital ones and zeroes that computers understand. This data, whether for a still picture or video, is then sent to the PC, where it's displayed on the screen.

Unlike still pictures, the acceptable level of quality of a moving video output from a webcam depends more on the 'frame rate' - the number of pictures that can be captuerd and displayed per second - than the actual image quality of each frame. But because each full-frame picture from a webcam contains several hundred thousand pixels - the equivalent of a low-resolution still photograph - the amount of data required to produce a chunk of video can be fairly large. In order to be able to transfer this using a standard USB connection, which works at 12Mbit/s, most cameras have to limit the frame rate. This is why video from a web cam isn't as smooth or highly detailed as the footage you'd get from a 'proper' digital video camera. To get round this, some cameras have internal circuitry to perform something called data compression. This squeezes down the amount of data the camera needs to send to the PC, mainly by stripping out information that isn't necessary to create a convincing video. This enables cameras to achieve slightly faster frame rates without the USB connection being overwhelmed.

So, all the webcam itself does is send video to your computer. To do anything useful with this stream, you'll need the right software. The one bare essential is driver software, which will enable other applications to decipher the raw digital data. Some less expensive webcams don't come with much more than that. This isn't too tragic, however - as long as you have video drivers, any other program that you may buy or download to do what you want should work fine with your webcam.

As well as the driver software, though, most webcams at least come with a basic video capture program to record video from the camera onto your hard disk in a standard video format, so that you can view it in multimedia player software such as Windows Media Player. For video conferencing, most webcams rely on Microsoft NetMeeting, which is built into all recent versions of Windows. If your computer is running Windows 98 SE, NetMeeting may not have been installed automatically, so you might have to dig out your original CDs and use the Windows Setup option in Control Panel, Add/Remove Programs.

Bear in mind that although they're called webcams, these cameras can't connect to the Internet by themselves:. You'll need to make sure you have a modem - or, if you want better-quality video calls, a broadband Internet connection.

What should I look for?

Before thinking about cool extras and whiz-bang gizmos, it pays to make sure the basics of your webcam are present and correct. The first thing to look for is image quality. This varies, and it's often hard to tell just by looking at the specs. But that, in a nutshell, is why we're here: take a look at the reviews overleaf. In general, though, go for the highest resolution you can get. A cam with a manual focus ring is also likely to give you better-quality images than one with fixed focus. Not all webcams come with a microphone, either.

There are three basic different types of webcam, and it pays to think about what you want one for before you take the plunge. Take a look at 'What can you do with your webcam?' for a few ideas. Some basic models are designed to be tethered to your desktop. Others are specifically designed to be used with notebook computers, and feature clips, grips and other cunning devices to attach them to the top of the screen. A few models have CCDs with a higher resolution than you'd need simply for capturing video. These often detach from their desktop stands and have their own built-in memory, enabling them to double as digital cameras. Bear in mind, though, that the digital still images you get out of them will be nothing like the quality of a dedicated digital camera - but then, they're nothing like the same price, either. Some webcams are sold on the basis of really specialised features, for instance the Veo Mobile Connect, which can connect to a network, enabling you to capture video to a remote PC. You'd only choose this kind of product if you had a specific use for it in mind.

Finally, but importantly, you should look at the software that comes with a webcam. This varies enormously, and it's one of areas that distinguish cheaper models from more expensive ones. Cheap webcams tend to come with a hotch-potch of third-party, cut-down or demo programs. More expensive models have easier to use, specially-written all-in-one software. Look out, too, for decent video and image editing programs, as these are usually quite sophisticated and expensive to buy separately.