Buyer's Guide 2007: Lens Strategy
How to select the right mix of lenses for your photography
WIDE ZOOMS AND FISH-EYE LENSES
In the 35mm film format, lenses with a focal length less than 40mm are usually considered wide-angle lenses. These wide lenses can spread a scene, allowing more elements into a photograph, which is especially useful in small spaces. They also increase the available depth of field, meaning a greater area can more easily be rendered in sharp focus.
Architectural photographers use wide-angles to show as much of a building's interior or exterior as possible, especially if working space is tight. Journalists often utilize wide-angles to show disparate elements together in one shot, such as the juxtaposition of a subject's reaction to activity elsewhere in the scene.
Once the focal length gets down below 20mm or so, the term ultra-wide-angle is commonly used. These lenses show an extremely wide angle of view-so much so that distortion comes into play. With rectilinear and aspherical glass, however, today's ultra-wides do a much better job of covering a tremendous area without amplified edge distortion.
Sometimes distortion can be desirable in a wide-angle lens. Fish-eye lenses, so dubbed because they often capture as much as 180 degrees or more, can be a fun way to create special effects by capitalizing on a bit of the distortion inherent in extremely wide lenses. Some fish-eye lenses are termed "full-frame" to denote that the image area still fills the full rectangular frame, while other fish-eyes are referred to as "circular" because they produce a perfectly round image in the center of the frame without a straight line anywhere in sight.
Sigma's new 8mm fish-eye lens, the ƒ/4 EX DG, is of the circular variety. This autofocus lens works equally well with film and digital cameras, and it has available mounts to fit Canon, Nikon, Pentax, Sigma and Sony bodies. The 180-degree angle of view makes the lens ideal for scientific uses in which precision measurements of an ultra-wide perspective are required. For photographers just looking to have some fun with a unique lens, the circular fish-eye makes a unique view of any composition.
For those photographers who want an ultra-wide lens that stops short of a fish-eye view, Tamron has introduced a new 11-18mm digital zoom. The SP AF11-18mm Di II LD (IF) is an aspherical lens with a variable maximum aperture of ƒ/4.5-5.6. It's a designed-for-digital lens, so it fits only the digital bodies from Canon, Nikon and Sony. But on those cameras, it offers the 35mm equivalent of 17-28mm coverage; that's an angle of view from 75 to 103 degrees.