Wondering whether or not the shutter speeds on your camera are accurate? Instead of taking it to a shop or buying expensive testing equipment, you can use an old television or CRT monitor as a simple shutter speed tester! Camera enthusiast Rick Oleson has an easy to understand diagram showing what you can expect to see from the screen at different shutter speeds. For a more technical explanation and tutorial, check out this article that appeared in a 1967 issue of Popular Science.
You already own a shutter speed tester [Rick Oleson]