Wide-angle photography opens up vast new vistas to the photographer, but “going wide” presents a special challenge to the digital-SLR user. That’s because the image sensors used in most D-SLRs are considerably smaller than a 35mm film frame and thus “see” a smaller portion of the image produced by any lens than that seen by a 35mm SLR. As a result, a given focal length produces a narrower angle of view when used on a D-SLR than when used on a 35mm camera.

Most D-SLRs that are based on the 35mm SLR form factor have image sensors that measure around 23.6x15.8mm, close enough to the 25.05x16.7mm dimensions of an Advanced Photo System C-format image frame that these are commonly known as “APS-C” format sensors. Cameras in this category include all D-SLRs from Fujifilm, Konica Minolta, Nikon, Pentax and Samsung, plus all Canon D-SLRs except the EOS-1D/Ds series and EOS 5D.

There are two basic solutions for wide-angle fans. You could buy one of the full-frame D-SLRs, of course (currently, the Canon EOS-1Ds Mark II or EOS 5D), on which all lenses frame just as they do on a 35mm SLR. The drawback here is that those cameras sell for around $7,000 and $3,000, respectively.

A considerably less costly alternative is to buy one of the inexpensive 18-55mm zoom lenses usually offered as part of a kit with entry-level D-SLRs. These are approximately equivalent to a 28-80mm zoom on a 35mm SLR, giving you definite wide-angle capability; they generally cost between $100 and $200. As a bonus, in most cases they were designed specifically for use with APS-C-sensor D-SLRs, optimizing image quality and keeping lens size down.

For really wide-angle fans, the D-SLR manufacturers and independent lens makers offer a number of very short focal-length zoom lenses optimized for use with APS-C-sensor D-SLRs. The accompanying chart lists these and other wide-angle lenses for D-SLRs, but essentially they start with a 10mm, 11mm or 12mm focal length, which on these D-SLRs is equivalent to 16-18mm on a 35mm SLR—extremely wide-angle. These are terrific choices for wide-angle fans because they provide everything from superwide-angle to moderate wide-angle in a single package, allowing you to adjust framing in tight spaces and minimizing the number of lens changes, which helps keep dust off the image sensor.

Each D-SLR manufacturer and independent lens maker gives its APS-C D-SLR lenses an identifying code. The Canon designation is EF-S, Nikon and Tokina are DX, Pentax is DA, Sigma is DC and Tamron is Di II. Because APS-C image sensors are smaller than a full 35mm image frame, lenses designed for cameras with these sensors don’t have to produce as large an image circle. This allows for smaller lenses that send light rays more directly into the image sensor’s pixels for better image quality, but means the lenses can’t be used on 35mm SLRs or full-frame D-SLRs, because they’ll vignette (in some cases, they can’t even be mounted on full-frame camera bodies).

The Olympus Zuiko Digital lenses are designed specifically for Four Thirds System D-SLRs (currently, the Olympus E-1, Evolt E-330 and Evolt E-500, and the new Panasonic Lumix DMC-L1), which have even smaller image sensors—17.3x13mm, with a 2x focal-length factor.

You can use compatible film-camera wide-angle lenses on your D-SLR, of course; they just won’t provide as wide an angle of view. With an APS-C format D-SLR, any lens of 24mm or shorter will provide noticeable wide-angle capability.

What To Look For
When choosing a wide-angle lens for your D-SLR, your first concerns are that the lens in question will provide the desired angle of view and work on your camera. If you’re used to 35mm SLRs, you can determine the focal length required to provide the equivalent angle of view by dividing the 35mm camera lens’ focal length by 1.5 for an APS-C-format D-SLR or by 2 for a Four Thirds System D-SLR: If you want an angle of view equivalent to a 24mm lens on a 35mm camera, you’ll need a 16mm lens on an APS-C D-SLR or a 12mm lens on a Four Thirds D-SLR.

Next, consider lens speed, special elements and focusing mechanism. Faster lenses are easier to focus manually in dim light and autofocus more quickly. They also provide a brighter viewfinder image for easier composing. But they cost considerably more than slower lenses of equivalent focal length. If you do a lot of low-light shooting, a faster lens will be worth the extra cost; otherwise, probably not.

Low-dispersion elements (identified by designations such as ED, LD, ELD, HLD, SLD, UD and SUD in the lens name) minimize chromatic aberrations and thus provide sharper images. Aspherical elements reduce spherical aberrations and edge distortion and provide more even illumination across the image area, providing better resolution and contrast, minimizing the curving of straight lines at the edges of the image and reducing darkened image corners and edges.

Internal- and rear-focusing systems move elements inside the lens instead of extending the front elements away from the camera body. In wide-angle lenses, internal focusing offers several advantages: The front element doesn’t rotate during focusing, handy when using orientation-sensitive lens attachments such as polarizers and graduated filters; moving smaller internal elements rather than heavier front ones makes for quicker autofocusing; and minimum focusing distances can be reduced. Aspherical elements and internal/rear focusing also allow for more compact lens designs.

Getting the Most from Wide-Angle Lenses
A wide-angle lens will take in a large slice of the scene before the camera. The biggest faults in wide-angle shots are lack of a center of interest and clutter. A wide vista with no visual center lacks impact, and the viewer’s eye tends not to know where to go. A landscape shot with interesting cloud formations or reflections in a lake can be lovely. But since it’s all at a great distance, the resulting image will have a flat perspective. After you shoot such a scene, look for an angle that includes a foreground subject that can add depth to the image—a tree or a rock formation. You can even position a travel companion strategically in the shot to add depth. Try to keep your wide-angle compositions as simple as possible. Too many elements in the picture just con-fuses the viewer.

Because a wide-angle lens takes in more of it, a tilted horizon line is especially annoying to the viewer, so be sure to level the camera. When photographing buildings or forests, remember that vertical lines in the image will converge toward the top if you tilt the camera up because the image (sensor) plane isn’t parallel to the subject plane—an interesting effect when you want it, but generally not desirable in architectural renderings.

When you have to get a whole group of people in a shot and can’t back up far enough due to a wall or cliff to do it, a wide-angle lens is just what you need. But here’s something to keep in mind: When using a really wide-angle lens, you’re picturing subjects directly in front of the camera quite differently from subjects at the edges of the frame. With a 90-degree (horizontal) angle of view, about what you’d get with an 11mm lens on an APS-C-format D-SLR or a 17mm lens on a 35mm SLR, the lens takes in subjects 45 degrees to each side. If you’re photographing a row of people lined up across the frame, you’re viewing the person directly in front of the camera square-on, but you’re viewing those at the edges of the frame at a 45-degree angle. You can largely solve this problem by having those on the ends turn toward the camera, so that the camera “sees” them all at the same angle.

Another concern is the distortion caused by picturing three-dimensional objects on a flat surface (the image sensor, in a digital camera). Those at the edges will appear elongated. This isn’t actually a result of lens distortion; it’s just a geometric fact of life when you project a three-dimensional object onto a flat surface at an angle. The best solution is to avoid compositions that include three-dimensional objects at the edges.

The most dramatic wide-angle photos are those made at close range. Move very close to a subject to render it very large in the frame, and the lens’ wide angle of view will still include some of the surroundings, exaggerating the subject’s size relative to its environment.