Like mixing chocolate and peanut butter, you've probably been tempted to try taking a picture of something on your CRT TV's screen with your digital camera. And while chocolate and peanut butter is a delicious combination, you may have had somewhat less successful results with your TV/camera experiment.
You probably got a picture that looked something like this. What happened? Well, a standard TV image is rendered from the top to bottom of the screen, one line at a time, about 30 times per second. So it's easy to see what went wrong: the picture was shot with a shutter speed that's too slow, so it caught the TV in the act of drawing the picture. Specifically, it caught the electron gun aimed somewhere in midframe, repainting the image, with a band of fading phosphors visible.
Shoot It Slow
Actually, the solution is simple. To catch a solid, complete image of the TV screen with your digital camera, you need to use a shutter speed of less than 1/30 second.
The easiest way to do that is to set your camera to its shutter priority mode (usually indicated by an "S") and use the camera controls to change the shutter speed until you see a speed of 1/15, 1/20, or 1/25 in the viewfinder. You'll probably find that choosing 1/30 on the nose is a little too fast; you'll still get a blank band somewhere in the frame. Go too slow, though, and the picture will start to blur simply from the motion in the video. I've found that 1/15 or 1/20 to be just about ideal for most situations. Here's a photo I captured at 1/20; it's a dramatic improvement over the first example, since I captured the entire image.
What if your camera doesn't have a shutter priority mode? Well, try the program mode. Usually, you can shift the shutter speed up or down by using the camera's controls--the aperture setting will change as well, ensuring that the exposure stays correct. Another alternative is to see if your camera offers a slow-shutter scene mode.
Mind the Details
That's the technique in a nutshell; now you know how to make a photographic record of the next time the Eagles concert airs. Then again, you could probably just buy the DVD instead. A better use of this newfound skill might be to add graphical punctuation on media commentary on your blog--or you could photograph your kid's high score while playing Zelda on the PlayStation.
But to get the best results while photographing images on your television, you should keep a few things in mind. A tripod will help get better results, for instance, since you're shooting at fairly slow shutter speeds and a shaky camera will make a blurry picture.
Also, shoot at night with the lights out, or draw the curtains during the day. Direct light on the TV screen will result in reflections and glare that can wash out the picture and create distractions.
Digital TVs Are Easier to Shoot
One last note about digital TVs, such as LCD and plasmas. These newfangled gadgets don't draw the picture on the screen in the same way as old CRT-based TVs. They create the picture using a mode called progressive scan, which means that the entire screen is refreshed simultaneously--no scan lines. So you don't have to worry about using a slow shutter speed on such TVs. Here's a shot of a plasma TV, taken at 1/60.