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Tuesday, February 26, 2013

Telephotos For Landscapes

Think Differently…

Labels: LensesGear
This Article Features Photo Zoom
While super telephoto lenses have relatively long minimum focusing distance, many of the lenses in our range can focus fairly close, providing the user with two ways to make "different" landscape images—to explore the whole other worlds of macro and telephoto. You can use the telephoto lens to isolate and compress distant portions of the scene or, to zero in on close portions for more image possibilities. Many such lenses are great for flower shots and even large insects. Some of the lenses in our chart are, in fact, true "1:1" macro lenses.

Different Nature
Wildlife photographers use long lenses—the longer and the faster, the better. Longer lenses provide bigger images of hard-to-approach subjects, while fast lenses permit using faster shutter speeds to minimize blur and lower ISOs to maximize image quality. But such lenses are big, heavy brutes and not easy to carry far afield.

Landscape shooters generally stop down to increase depth of field, so a fast maximum aperture isn't necessary; they can make do with slower, smaller and lighter lenses that are easier to carry deep into tough terrain: a 70-200mm ƒ/4 rather than a 70-200mm ƒ/2.8, for example.

Slower lenses also generally take smaller filters, which cost less than larger filters and take up less space in the camera bag. Wildlife photographers also demand quick, accurate autofocus (AF) performance—never a bad thing, but not as important to landscape shooters, who often focus manually.

Sensor Size And Focal Length

Cameras with smaller-than-full-frame sensors include in their specs a focal-length or "crop" factor: 1.5X for APS-C (1.6X for Canon APS-C); 2X for Four Thirds. That means that a given lens on one of these camera's frames is like a longer lens on a full-frame camera, because the smaller sensor sees less of the image produced by the lens. For example, a 100mm lens on an APS-C camera frames like a 150-160mm lens on a full-frame camera. A 100mm lens on a Four Thirds (or Micro Four Thirds mirrorless camera) frames like a 200mm lens on a full-frame camera.

A given lens produces an image of a given size at the image plane when focused at a given distance. This size doesn't change because you put a larger or smaller sensor at the image plane. What changes is how much of the image the sensor "sees" and thus, how large in the frame a given subject appears. A smaller sensor doesn't increase focal length (100mm is still 100mm) or magnification; it only changes the "crop."

From a practical standpoint, however, you can think of the crop factor as magnification: Putting a 300mm lens on an APS-C camera will produce an image that's framed like one produced by a 450-480mm lens on a full-frame camera, and the subject's image will appear larger in the frame because of the tighter cropping.


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