Webcams

Last updated: May 11, 2010.

Ever wanted to run your own TV station? A webcam lets you do just that. With one of these tiny, bug-eyed cameras hooked up to your computer, you can broadcast pictures of yourself or your home to the entire world! A webcam is a bit like a digital camera and works much the same way. But unlike a digital camera, it's designed to make relatively compact digital photos that are easy to upload onto Web pages or send across the Internet. It all sounds simple enough, but how do webcams actually work? Let's take a closer look!

Photo: The Microsoft LifeCam VX-1000 webcam can stand on a table or clip to the screen of a laptop. It has a built-in microphone and a long USB cable carries both picture and sound to your computer. Some laptops and netbooks have built-in webcams. That sounds like a good idea in theory but, again, it limits you to showing pictures of what is directly in front of the computer. Other popular cams are made by Logitech, Creative, Hue, and TeckNet.

How does a webcam work?

A webcam is a compact digital camera you can hook up to your computer to broadcast video images in real time (as they happen). Just like a digital camera, it captures light through a small lens at the front using a tiny grid of light-detectors, known as a charge-coupled device (CCD). The CCD converts the picture in front of the camera into digital format—a string of zeros and ones that a computer knows how to handle. (You can find out exactly how this happens in our article on CCDs.) Unlike a digital camera, a webcam has no built-in memory or flash memory card. It's designed to capture pictures and transmit them immediately to a computer. That's why webcams have USB cables coming out of the back. The USB cable supplies power to the webcam from the computer and takes the digital information captured by the webcam's CCD back to the computer—from where it travels on to the Internet.

While a good digital camera is designed to capture high-resolution (finely detailed) pictures, a webcam deliberately captures much lower resolution (more blurred, grainy, and "pixelated") images. A typical webcam makes image files that are about one tenth the size of a typical digital camera. That means webcam snapshots can be sent over the Internet much more quickly than large digital photos.

There are two main reasons why you'd want to send pictures in this way. You might want to publish a frequently updated still image of a particular place for others to view on the Internet. For example, a zoo might publish live pictures from its zebra or giraffe house. Or you might want to video chat with a friend using an instant messaging program, such as Skype or Live Messenger.

Webcam stills

Photo: A Logitech Quickcam laptop webcam. The USB cable curling out of the camera has two jobs: it takes power to the cam from the computer and then carries the pictures from the cam back the opposite way.

Suppose you want to broadcast images of your garden on a website and update them at regular intervals. You can do that with a webcam. You simply point the cam at your garden, hook it up to your computer, and install a special piece of software. The software captures an image from the cam every five minutes (or at some preset interval) and copies it onto your website using a simple process called FTP (file-transfer protocol). Every time a new image is uploaded, it replaces the previous one on your website. When people look at your site, they see the latest image that your cam has uploaded. Most people design their cam pages so they "refresh" (automatically reload) every few minutes. That ensures they're always showing the latest images.

Here are some examples of webcams that work this way:

• Marwell Zoo: "There are currently four webcams for you to view. Visit the Giraffe house, or see if you can spot a Tiger, Meerkat or a Penguin!"
• Lamb Cam: Watch Farmer Bob and his lambs live.
• Panda Cam: Check out the Wolong Panda cam in China.
• Cruise cams: Watch the view from a Princess ocean liner at sea.

Video chat

Now many more people have broadband Internet connections, webcam videoconferencing (or video chat) has become very popular. Using webcams and computers, you can talk to your family and friends anytime, anywhere in the world. To chat to someone like this, you both need a webcam and you both need to be running a video chat program on your computer. Examples include the MSN, Yahoo, and AIM instant messaging programs, and Skype.

Video chat programs work just like still webcams—only they're uploading photos constantly. Suppose I am video chatting with you. My camera captures a picture of me, turns it into digital format, and sends it my computer. The chat program on my machine streams the image information across the Internet to your computer. The chat program on your machine receives the image information and converts it back into a picture, which it displays on your screen. Meanwhile, your camera is doing exactly the same thing with a picture of you and sending it in the opposite direction. This two-way process happens constantly, so each of us gets a constantly updated picture of the other. To speed things up, video chat programs like Skype make a direct connection between your machine and mine, bypassing centralized servers. This very efficient way of using the Net is called P2P (peer-to-peer) networking. You can read more about it in our article on how the Internet works.