Figure 1-38.–Variable focal-length (zoom) lens.
variable focal length from about 35mm to 70mm. They
are usually small and lightweight. They are designed to
be used instead of a normal focal-length lens, not to
replace a range of focal length lenses.
Long-range zoom lenses start at about 35mm and
include the popular 100mm or 105mm focal lengths.
They can take the place of four, fixed focal-length
lenses: the 35mm, 50mm, 85mm, and 105mm.
Telephoto-range zoom lenses have focal lengths
that range from about 50mm to 135mm, 90mm to
23Omm, 75mm to 150mm, and even 135mm to 600mm.
The most popular telephoto zoom is from about 80mm
to 200mm.
Now you have some basic knowledge of the way
light reacts when striking various objects. You also
know how it forms an image through a lens. With
practice, you will be able to apply these principles in
photographic practices. By using various focal-length
lenses and aperture settings, you can control image size
and depth of field as well as the apparent perspective of
your photographs. In the next chapter, light-sensitive
materials are discussed. This will enable you to record
permanent images.
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