Friday, January 12, 2007
Wide-Angle Lenses For Digital
Yes, you can do wide-angle photography with a D-SLR!
|The widest-angle lenses are the fish-eyes. These provide a 180-degree angle of view and come in two varieties: circular and full-frame. Circular fish-eyes produce a round image in the camera's standard rectangular image frame; full-frame fish-eyes fill the frame, producing a 180-degree angle of view measured from corner to corner.|
The only circular fish-eye on the market today is Sigma's 8mm ƒ/4, and it produces a circular image only with full-frame cameras (35mm SLRs and full-frame D-SLRs). On APS-C D-SLRs, the image frame cuts into the top and bottom of the circular image. (Sigma recently announced a new optimized-for-digital version of this lens, but it produces the same framing with APS-C D-SLRs.)
Three full-frame fish-eyes have been designed especially for APS-C D-SLRs: the Nikon 10.5mm ƒ/2.8, the Olympus 8mm ƒ/3.5 and the Pentax 10-17mm ƒ/3.5-4.5 fish-eye zoom. You can use full-frame fish-eye lenses designed for 35mm SLRs on D-SLRs, but that 1.5x magnification factor greatly reduces their impact.
Focal lengths for full-frame fish-eyes overlap focal lengths for rectilinear ("regular") superwide-angle lenses. The difference is that rectilinear lenses are corrected for barrel distortion and (in theory) render straight lines as straight lines no matter where they pass through the image. Full-frame fish-eyes exhibit barrel distortion and curve all straight lines in an image except those that pass through the center of the frame. And, of course, the fish-eyes have that 180-degree (diagonal) angle of view, compared to around 115 degrees for an equivalent-focal-length rectilinear lens.
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.
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