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Tuesday, August 1, 2006

Mastering The Wide-Angle

Exploring with the wide end of the focal spectrum opens up a world of creative compositional possibilities

Using Wide-Angle Lenses

There are three main reasons why photographers use wide-angles: to include a vast vista in the image, to get subjects in the frame when space is limited and it's impossible to move the camera farther away, and to produce wide-angle distortion effects by moving very close to a subject.

When photographing wide vistas, remember that TTL metering might not work as it does with longer lenses. If you're shooting with a D-SLR, check the image on the LCD monitor after shooting it to confirm that the exposure is what you had in mind; if shooting film, bracket exposures until you get a feel for how your wide-angle lens works with your camera's metering system(s).

If you tilt a camera up or down, vertical objects at the sides of the image will tilt into the image. And if you don't hold the camera level horizontally, the horizon line will tilt. With longer focallength lenses, you might not notice this, but with their broad fields of view, wideangle lenses emphasize these effects. So keep the camera level (a tripod helps here) unless you specifically want tilted edge objects or horizon lines.

Wide-Angle Distortion

The elongated, distorted effect produced by moving in very close with a wide-angle lens is actually an accurate rendering of perspective for that shooting distance. The effect looks odd because we don't normally view subjects from such close range, but it's real. Perspective— the relative sizes of objects in a photo and the apparent distances between them—depends on the shooting distance. Move closer, and everything in the scene becomes larger, but nearer subjects "grow" faster than more distant ones, while the apparent distance between them increases: wide-angle distortion.

Conversely, if you move farther away, everything in the scene will get smaller, nearer subjects will shrink more rapidly relative to farther ones, and the apparent distance between them will decrease: the telephoto compression effect. This occurs regardless of the focal length of the lens on the camera— move far back with your wide—angle lens, then enlarge the central portion of the image on-screen or in a cropped print, and you'll get telephoto compression with your wideangle lens.

The expansion effect is most noticeable when wide-angle lenses are used because we generally move close to the subject when shooting with a wide-angle lens. And because of its wider angle of view, the wide-angle lens lets us movein closer than with a longer lens and still get the whole subject in the frame. Conversely, the compression effect is most noticeable when long lenses are used because we generally shoot from relatively far away when we use long lenses.

Wide-Angle Flash

Like lenses, flash units have specific angles of coverage. If you're using flash with a wide-angle lens, check the specs to make sure the flash unit will cover what the lens sees—the area that will appear in the photo. Otherwise, you'll get a photo with a properly exposed central area and too-dark edges. Also, remember that illumination from direct flash falls off as the square of the distance: a subject twice as far from the camera as the properly exposed main one will be underexposed by two stops. The closer you move to a subject with the wide—angle lens and flash, the greater the exposure difference there will be between the main subject and background ones.

Depth Of Field

All other things being equal, wideangle lenses provide more depth of field than longer ones. That means that at the same focused distance and ƒ-number, a shorter lens will provide much more depth of field than a longer one. As noted, however, we generally move closer when shooting with a wide-angle lens, so all things aren't equal. At a given reproduction ratio (magnification) and ƒ-number, depth of field is the same for any focal length, assuming the lenses are all used on the same-format camera.

Stopping the lens down increases depth of field; in fact, the aperture is our most frequently used means of controlling depth of field. With a short lens, stopping the lens down results in very tiny apertures: While a 100mm lens at ƒ/22 has an aperture diameter of 4.5mm, a 10mm APS-C lens at ƒ/22 has an aperture diameter of just 0.45mm—less than 1/50 of an inch.


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