Behind the Lens: Optimizing shutter speed

At a Republican rally Tuesday, Nov. 2, 2010 I used a flash in a dark conference room. To allow ambient light to influence my exposure, I selected a slow 1/30th shutter-speed. Most point-and-shoot cameras will do something similar with a flash setting called 'slow-sync'. Notice how this technique caused blurring in the woman's hand at right from the two light sources. .

At a Republican rally Tuesday, Nov. 2, 2010 I used a flash in a dark conference room. To allow ambient light to influence my exposure, I selected a slow 1/30th shutter-speed. Most point-and-shoot cameras will do something similar with a flash setting called 'slow-sync'. Notice how this technique caused blurring in the woman's hand at right from the two light sources. .

A former Journal-World colleague recently told me she’d purchased a camera I had mentioned in this column. Some early results, when using the camera’s built-in flash, had been disappointing. According to her and her husband, the flash washed-out the subject, ruining images. I felt somewhat responsible since I had touted the camera as having some unique features. Many improvements and features have been added to cameras, but not a lot of advances have been made in the quality of built-in flashes on consumer point-and-shoot cameras. It’s difficult for me to determine the exact problem in a situation like hers without accessing the same camera and being in the same situation or environment the photo was taken. However, assuming the camera was operating correctly, I’ll list some inherent problems and possible solutions with these types of flashes.

On the majority of point-and-shoot consumer cameras, the built-in flash is located near the lens and aimed straight ahead. You can’t redirect or easily diffuse the light. This alone creates an unpleasant, unflattering light and is one reason I prefer people avoid using it if at all possible. The other thing that happens when you turn on your flash is that the camera automatically sets a shutter-speed to sync with the flash. This may be as slow as 1/60 of a second or as fast as up to 1/200 of a second. These shutter-speeds may be too fast to allow ambient light to influence the exposure. So while the flash will certainly illuminate a foreground subject, the background, minus all ambient light, will tend to look darker. In addition, the direct flash will cast a shadow on everything behind the subject. These elements can lead to flash-lit subjects that appear washed-out and possibly overexposed.

One solution is to find the “slow-sync” setting available on most cameras. Some cameras may show this as a “party” or “night” mode. Slow sync instructs the camera to select a shutter speed appropriate for an exposure based on the ambient light and the flash together. This can result in a much more pleasing and natural appearing image. Keep in mind that if there is very little ambient light to start with your shutter speed may be longer than you can hold the camera steady. While this can result in some blurring or “ghosting” in your image, it can make for more interesting and better illuminated photos than the typical “deer-in-the-headlights” flash-only shots.