Telephoto Lens
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Telephoto Lenses
By definition, a telephoto lens
is one whose focal length is greater than that of a normal lens. The longer the
focal length of the lens, the greater the degree of magnification. In fact, the
magnification is mathematically related to focal length. For example, a 100mm
lens produces an image exactly twice that of a normal lens. A 400mm lens gives
you an image size eight times your normal lens.
As the lens lengthens,
some interesting things happen. The len's angle of view becomes narrower and
depth-of-field becomes shallower. A narrow angle of view enables you to isolate
a detail in a distant building or eliminate a cluttered foreground. A shallow
depth-of-field is great for blurring distracting backgrounds so that attention
is directed towards your subject such as an outdoor portrait.
By far,
the most useful telephoto lenses are those with medium focal lengths...between
85mm and 200mm. Because they minimize facial distortion and allow a comfortable
distance between photographer and subject, medium telephotos are ideally suited
for portraits. In addition, they are perfect for many other situations in which
you have to keep a moderate distance from your subject such as candid street
shots or animals at the zoo.
Telephotos lenses of 300mm or longer are
usually for specialized demands and would be too powerful for ordinary usage.
However, if you have a keen interest in wildlife photography or prefer huge suns
in your sunset shots, then these and longer lenses may be for you. For the
occasional "long reach", a tele-extender combined with your telephoto will work
just fine.
Remember, because the magnification of telephoto lenses
accentuates the effect of camera movement, faster shutter speeds are required.
To obtain a sharp picture, the rule of thumb is to use a shutter speed closest
to the focal length of the lens. For a 135mm lens, handhold at no slower than
1/125 second. With a 200mm lens, you should be at 1/250 second. If slower
shutter speeds are needed because of low light or small aperture requirements,
better get out your tripod.
So "reach out" to new and exciting
photographic horizons...with telephoto lenses!
Copyright ©
Monte Nagler 2001. All rights reserved.
