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Sunday, August 1, 2004

Lenses [And The Landscape]


Film Vs. Digital | Zooms | Wide-Angles | Telephotos | Zooms Vs. Fixed


Because so much of the scene is captured by such lenses, it's easy to include too much in the photograph. With this all-encompassing range, an image can have so many details that the viewer is unable to focus on any central point.

Rather than simply getting in as much as you can within the frame, consider traditional compositional elements, such as leading lines, contrasting textures, highlights and shadows, to draw attention to the most important parts of your scene. Although this is applicable to any focal length, it can be particularly important when using extreme wide-angle lenses.

[ Telephotos ] Telephoto lenses bring distant objects closer. Moderate telephotos, ranging from 85mm to 200mm, and super-telephotos of 300mm and longer, have a narrow field of view that creates an emphasis on individual details that otherwise might be lost with a wider focal length.

Another inherent quality of the telephoto lens is an optical effect called compression. Compression gives the impression that objects appear closer to each other than they actually are. This effect creates a sense of proximity between distant objects that can serve as a means of contrasting elements in a scene. You could isolate a stand of trees against a distant mountain range and create a sense of scale, for example.

Compression can be useful for capturing a variety of textures or patterns that exist in a scene. In a photograph taken in the desert, for example, the frame can consist of a pristine foreground of sand, the undulating rise and fall of the dunes and the rising mountain ranges in the background. These elements are compressed and isolated by the telephoto lens, resulting in an image where the different textures and shapes serve as contrasting elements in the final photograph.

Compression also can be used effectively with contrasting tones in an image. If a scene includes a group of white aspens in front of a darker stand of trees, the proximity created by the telephoto lens boosts the difference in color and tone, producing a shot with significantly more impact than might be achieved with a wider focal length in the same camera position.

By knowing your lenses when composing landscape images, you'll have what you need to create a piece of art rather than a snapshot.


[ Zoom Vs. Fixed Lenses ]
It used to be that fixed focal-length or prime lenses were considered far superior to zooms. That's no longer the case. Many zoom lenses offer optical quality comparable, if not superior in some cases, to their prime siblings. So why choose a fixed focal length over a zoom? There are several reasons.

The first one is speed—not how fast the lens can focus, but rather the lens' maximum aperture. Many fixed focal-length lenses offer a maximum aperture of ƒ/2.8 or ƒ/4. For example, a fixed 300mm ƒ/4 lens will provide a full stop of light more than a 100-300mm ƒ/3.5-5.6, which has an effective aperture of ƒ/5.6 at its 300mm setting.

Hence, the lens gathers more light for a brighter image in the viewfinder and maintains an exposure with a higher shutter speed under low light conditions. In addition, because more light is coming through the lens and reaching the AF sensor, the camera has a better chance of quickly achieving autofocus.

Variable-aperture zoom lenses transmit less light whenever you create its telephoto range. For example, a 24-120mm ƒ/3.5-4.5 lens starts off with a relatively wide aperture, but by the time it reaches its 120mm focal length, you've lost almost a full stop of light. This means that if you were shooting at a shutter speed of 1/30 sec., you'd have to decrease the shutter speed to 1/15 sec. to maintain the same exposure. You'd likely end up with a soft image because of camera motion or even shutter vibration.

There are zoom lenses with a constant aperture, but generally they're considerably more expensive than their variable-aperture versions. If you can afford them, they're a worthwhile investment, especially since you're shooting
during dusk and dawn in most landscape photography.

Fixed focal-length lenses also are subject to less spherical aberration, such as pincushioning and barrel distortion. Appearing as bowing toward the edges of the frame, these distortions usually are evident with wide-angle zoom focal lengths, where straight lines are slightly curved inward (pincushion) or outward (barrel). Although highly corrected, some zooms do better than others in this respect.

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