by Chris Woodford. Last updated: July 12, 2013.
Ever wanted to run your own
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.
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.
There are more pictures of this camera in our article on CCDs.
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:
- BBC England webcams: Lots of interesting scenic cams hosted by the BBC.
- 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!"
- Cruise cams: Watch the view from a Princess ocean liner at sea.
- Surfcams in Australia: There's often great live footage of surf spots here!
- Mount Everest Webcam: It's sometimes hard to make out much of a picture, but pretty remarkable that we can see anything from this location at all!
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.
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!