See the light: A quick guide to using flash in photos

It's not always obvious when you should use your pop-up flash, and when you should keep it turned off

Published: March 07, 2014 09:00 AM
In this low-light situation, I turned my camera's flash off.

To flash or not to flash? That's a question we should ask more often when shooting photos. Many of us simply choose Auto mode and let the camera decide whether to pop up the flash or not. But the camera doesn't always "know" the right answer. Here are two examples of that. 

True or false? Shooting outdoors on a bright, sunny day at high noon, the camera correctly skips the strobe because there's plenty of light.

False. The blazing sun will cast shadows, so you might need the flash to shed enough light on the subject's face, for example. But in auto mode, the camera’s flash won’t fire on its own, so you'll have to activate it manually.

True or false? Family and friends are gathered around a birthday cake in a darkened room as the birthday girl or boy prepares to blow out the candles. Since it's dark, the camera will automatically pop up the flash, which is the right thing to do.

False. That will destroy the soft atmospheric light coming from the candles on the birthday cake. In this case, the better option is to keep it turned off.

Know your camera's flash icons

To use your flash effectively, first determine how to turn it on and off. Almost all cameras have the following settings: Auto Flash (this lets the camera determine if the flash should be on or off); Fill Flash (this keeps the camera's flash always on and uses it for every shot); and Flash Off (which keeps the strobe turned off no matter how dark the setting).

One other common flash setting called Slow Sync Mode fires the camera's flash but then leaves the camera's shutter open longer than it would in Auto Flash mode. This lets you keep the natural or ambient light in the background while the flash illuminates your main subject. But because the shutter speed is slow, your subjects may appear blurry if they are in motion.

Four common flash options: auto flash, fill flash, flash off, and slow sync flash.

For more on advanced cameras and point-and-shoots, check our buying guide and Ratings for cameras.

When to use your pop-up or onboard flash

In most cases, you'll want to fire your camera's flash when shooting subjects at night or in dim lighting. This, of course, illuminates the scene. It can also be helpful on bright, sunny days—say, by the pool or on the ski slopes—when powerful light from the sun can create shadows, which can be distracting on your subject's face.

Another common scenario in which a camera's flash can be helpful is in a backlighting situation. For instance, say the subject is standing in front of a window. If you don't use the flash, you'll end up with a dark, silhouetted subject in front of a bright background. But leaving your flash off in a backlit situation can create an interesting effect, as illustrated by the photo of my son at the aquarium, above.

When photographing a flat, reflective surface, shoot at an angle (right) to reduce glare.

When not to use your pop-up or onboard flash

If you want to maintain the precise quality of the ambient, atmospheric light, even in a dim setting or at night, don't turn on your flash. (But consider using a tripod, especially if the shutter speed will be longer than a 1/60th of a second.)

Another common mistake is something you'll often see at evening sporting events or even in large school auditoriums: Flashes are popping off all around, but most onboard flashes aren't powerful enough to reach the field or stage and make their way back to the camera. In such situations, consider keeping the flash off, unless you're sitting close to the subjects.

Avoid using the flash at a zoo or aquarium, since it tends to bounce off the glass, and you end up with a burst of light in the middle of your picture. If you need to use the flash, don't stand perpendicularly to the glass. Position yourself at an angle to avoid seeing the light of your flash reflected in the glass.

Also, avoid using it in art museums or art galleries (the light can damage works of art), or at occasions such as weddings or religious ceremonies where subjects might be sensitive to a flash going off.

As you can see, it's not always obvious when to use a flash and when to do without it. Experiment and practice to see what results you get in different scenarios.  

When in doubt, take lots of photos with and without the flash if possible. You'll have a better chance of getting the exposure that will do justice to your subject. 

—Terry Sullivan

Shooting a flash photo directly into glass or a mirror can result in a poor photo.

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