Wide Open! Large-aperture magic

You should always shoot with your eyes wide open (at least, the one looking through the viewfinder). But often it pays to shoot with your lens wide open, too.

Wide apertures let in more light, so you can use a faster shutter speed in any given light level. This is handy for anything from low-light photography to action shooting.

Left: In this shot, selective focus directs the viewer's attention to the subject's eye(s). This was made with AF SLR, using a telephoto lens set at its widest aperture and closest focusing distance.
Right: If the background is considerably darker than the subject, you can use exposure to mask distractions. Photos byLynne Eodice

Another benefit of shooting wide open is very limited depth of field. If you're shooting a portrait, and the background is distracting, and you can't move the subject or camera, just open the lens to its widest aperture, and the background distractions will magically blur into insignificance. This effect is greatest when you use a longer focal length and shoot at a close focusing distance--shoot a head shot from 4 feet away with a 100mm lens wide-open at f/2.8, and background distractions will vanish.

You can use this limited depth of field for more than just making background distractions go away. Through the technique of selective focus, you can direct the viewer's attention precisely to where you want it in the image. The eye is drawn to what's sharp; focus carefully and throw everything else out of focus, and the viewer can't help but be drawn to the subject. For example, in a close-up of an animal, you can direct the viewer to the subject's eye(s) by focusing there and throwing the rest of the head out of focus.

This image takes advantage of selective focus and the lens-like properties of a glass of water. Noted pro Bert Stern made this "wine-glass" technique famous back in the 1950s with his great image of an Egyptian pyramid reflected in the wine, but you can produce the effect with plain water and any handy local subject. Move in close to the glass and focus on the image in the water, and use the camera's depth-of-field preview to select the aperture that provides the degree of sharpness or blur you want. For this image, the photographer just set the glass on the window sill of a high-rise office building, and recorded the image of the building next door. Early-morning sunlight provided warm colors, but you might try adding food coloring to the water in the glass for a different effect. Photo by Mike Stensvold

You can also spice up a flower close-up by including a foreground element and blurring it via selective focus. Just be sure the out-of-focus element enhances the image and doesn't distract from the main subject.

Photographing this Muscovy duck from close range with the lens wide open blurs the distracting background so it's no longer distracting (tight cropping also eliminates much of the distracting background), and the limited depth of field is adequate to cover the subject in profile, yet direct the viewer's eye to the subject. Canon EOS 20D digital SLR, 300mm f/4L lens, ISO 400; the exposure was 1¼1000 at f/4 (wide open). Photo by Mike Stensvold

Of course, there are drawbacks to shooting wide open. Limited depth of field can be a good thing, as just explained. But it can also be a bad thing, if you need great depth of field for a shot (in that case, use a faster film or set a higher ISO on a digital camera, and stop the lens down). And various lens aberrations are more evident when the lens is wide open, resulting in reduced image quality. But all in all, today's name-brand lenses perform very well wide open, and the benefits far outweigh the drawbacks. Give it a try!

In this shot, selective focus directs the viewer's attention to the subject's eye(s). This was made with AF SLR, using a telephoto lens set at its widest aperture and closest focusing distance. Photo by Mike Stensvold