Black-eyed Susans (#AT0044)
Footnote 2, the Basics: Interchangeable Lenses
Depending on the focal
length, lenses are referred to as either normal, wide-angle or telephoto.
Normal Lens:
In days of old, when you purchased a new 35 mm camera, it inevitably came
with a “normal” or 50 mm lens attached.
The 50 mm lens is “normal” because it sees the world in approximately
the same dimensions, as does the human eye.
Objects are not distorted through either shrinkage, as they are with
smaller wide-angle lens, nor magnified as will happen with a larger telephoto
lens.
Wide-angle Lens: Any lens with a focal length smaller than 50 mm.
Popular wide-angle lenses include those with focal lengths of 35 mm, 24
mm and 20 mm. A wide-angle lens
tends to shrink objects within the landscape, but can create a sense of expanded
depth. As mentioned in Tip # 4, the
24 mm wide-angle lens is my preferred lens for capturing the sweep of wide-open
country such as that found in the deserts, prairies and mountains of the
American west. One concern is that
any objects that form vertical lines, such as trees, will appear to lean
together if the film plane (the back of the camera) is not kept perfectly
parallel to them. This leaning inward may either be seen as a distortion or as a
creation of artistic expression depending on the circumstances and the viewer.
Telephoto Lens: Any lens with a focal length greater than 50 mm. Popular telephoto lenses include those with focal lengths of 200 mm, 300 mm, and 400 mm. A telephoto lens can “bring in” or magnify a bull elk or can lend drama to a mountain landscape by compressing the “waves” of mountain ridges, causing them to appear closer together than they actually are. Concerns regarding the use of telephoto lenses include the necessity of longer exposure times (light must pass through the “tunnel” of the longer lens) than with normal or wide-angle lenses. This concern is compounded by the fact that moderately priced telephoto lenses will have a low-end f-stop that is not very low (i.e. f/5.6 on 300 mm lens compared with f/1.8 on a normal lens). Shop for a 300 mm lens with a low-end f-stop of say 2.8 and you will see the price soar majestically through the roof. The low-end f-number is important because so many of the opportunities to photograph wildlife occur in the low light of early evening or early morning.
Another concern when using a telephoto lens is vibration. Since these are longer and heavier lenses, the smallest “shake” will result in a blurred image. Not long ago, “shutter shake” was of particular concern. This was brought about by the vibration caused when the little mirror that allows through-the-lens viewing of the composition, flipped up and out of the way during shutter release. Refined design and engineering has done away with the problem of shutter shake in modern cameras. But vibration in general remains the enemy, and the use of a tripod and cable release (or the self-timer on you camera) can help nullify the problem in low-light situations. The use of faster film (i.e. 200 ISO film) can also help.
Zoom Lens: Unlike “fixed” lenses, zoom lenses offer a continuous range of focal lengths. Historically, there was great concern that the optical quality of the “zooms” was below that of fixed lenses and many professional stayed away from them. With more refined design and engineering, this concern seems to be a thing of the past. The lightweight convenience and quality of modern zoom lenses are making them increasingly popular.
Macro Lens: These differ from other lenses in their ability to focus on close objects. Some things to know about macro lenses are: (1) the focal length of a macro lens, unlike a telephoto lens, does not determine the amount of magnification of the subject so much as how far you must stand from that subject to achieve the same amount of magnification. You can stand further away with a 200 mm macro lens to achieve the same close image of that hummingbird hovering by that beautiful red flower, than you can with a 50 mm or 100 mm macro lens. (2) There is very little depth of field allowed with a macro lens. Not many subjects in nature provide a perfectly flat field of vision, so the absence of any depth of field can be a problem. On the other hand, there are many beautiful photographic compositions where a single flower (or an individual part of a flower such as a stigma) stands out against a blurred background. (3) The final consideration that I’ll mention is that there are many viable and less expensive alternatives to macro lenses now available. Many zoom telephoto lenses now have close-focusing capability. The turn of a ring or flip of a switch converts such a lens into a “quazi” macro lens. Also, see Tip # 37 regarding close-up filters.
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