Who Set Harry on Auto Flash?By Mike Pasini, Editor
Imaging Resource Newsletter
If you've got a digicam, you are no Muggle, the magically-challenged inhabitants of Harry Potter's world. Why? Because you, like Harry, have a thunderbolt.
Harry got his on his forehead when, as an infant, he vanquished the evil You-Know-Who.
You get yours in your status display to help you set your flash options. Both
are forces against darkness, but yours recycles faster.
It also has some handy options.
The mode with which you are no doubt most familiar is the Auto Flash. It fires the flash whenever the meter decides there isn't enough light to make an exposure with the lens wide open and the shutter as slow as it will go. Auto flash is so handy it's probably the default setting on your digicam.
It can rob you of some beautiful low-light shots, however. And it can be very unwelcome in light-controlled environments like theaters and museums.
Cameras that sport onboard flash often include a red-eye reduction mode. In low-light situations, firing a flash into wide-open pupils illuminates the back of the eye, causing a You-Know-Who-like red stare. To reduce the effect, the flash can be fired rapidly a few times before the shutter is opened to trick those dilated pupils into contracting.
To be a good citizen, you have to have control of your magic and that means not using it sometimes. Turning off the flash will force your camera to take the shot with available light.
A flash exposure is different from an available light exposure. We owe the difference to Harold Edgerton, the MIT professor who invented the stroboscopic flash to take stop-action photographs. By developing a source of illumination that "flashed" on and off more quickly than a shutter, he was able to capture a hummingbird in flight, the corona of a drop of milk, and bullets on impact.
When you shoot with flash, the room can be entirely dark. It doesn't matter because the strobe provides not only the illumination but the exposure. It is quicker than your shutter.
But slow synch can combine a bit of natural light exposure with the flash. It simply leaves the shutter open longer than the strobe needs to fire. And that can add detail to the background in your image.
You don't have to go to Hogwart's with Harry to learn how to use your flash settings. But they are powerful magic.
This article is reprinted from The Imaging Resource Digital Photography Newsletter,
Beginner's Flash Column, published July 14, 2000
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