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Microsoft LifeCam VX-1000 webcam on a table

Webcams

by Chris Woodford. Last updated: July 12, 2013.

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: This 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 chip or flash memory card: it doesn't need to "remember" pictures because it's designed to capture 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.

Inside a webcam

Oh you know me, I just can't help taking things to pieces. So when I found a broken Logitech webcam, I couldn't resist! Getting the plastic case off proved almost impossible. But once I'd succeeded, here's what I found inside.

You can see that the webcam is little more than a plastic lens mounted directly onto a tiny electronic circuit board underneath. The lens screws in and out to increase its focal length, controlling the focus of your cam.

Parts inside a Logitech notebook webcam

Now take the lens off and you can see the light-sensitive CCD chip: it's the square thing in the middle of this circuit. Only the tiny, central part is light-sensitive: the rest of the CCD chip is concerned with connecting the light detector to the bigger circuit that surrounds it.

CCD inside a webcam

There are more pictures of this camera in our article on CCDs.

Webcam stills

A Logitech notebook webcam

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:

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 (VOIP) Voice Over Internet Protocol and is an example of what's known as P2P (peer-to-peer) networking. You can read more about it in our article on how VOIP works.

Can I use my digital camera as a webcam?

If you've got a digital camera already and a webcam is essentially the same thing, it might occur to you to use your ordinary cam as a webcam. Some digital cameras even have a built-in webcam button or mode making it very easy. For others, you'll need to find out if there's a driver available (that's a small file that tells your computer how to use a plug-in device in a certain way). Sometimes people write their own programs and drivers and make them available online for others, so Googling something like "use canon ixus as webcam" will often bring up helpful results.

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However, there's one thing you do need to be very wary of. A USB connection contains a 5-volt power supply as well as a data connection to and from your computer. Plug a digital camera into a USB socket on your PC and it will draw power the whole time it's connected. Digital cameras are not normally meant to be plugged into computers for more than a minute or two at a time (while you're uploading your photos). Leave a camera plugged in for a long time (half an hour or a couple of hours) while you're using it as a webcam and it can heat up considerably, either damaging the camera or overcharging the batteries. Consider that a good digital camera costs perhaps 10–50 times more than a basic webcam and you'll see what a risk you're taking. The message is simple: if you plan on using a webcam regularly, or for any length of time, buy a proper USB webcam. They're not expensive (you can get one for less than $20/£10)—and you'll save damage to your digital camera, which probably was expensive!

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Text copyright © Chris Woodford 2007, 2012. All rights reserved. Full copyright notice and terms of use.

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Woodford, Chris. (2007) Webcams. Retrieved from http://www.explainthatstuff.com/webcams.html. [Accessed (Insert date here)]

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