45
Chapter 3 Lenses
by a factor of 1.4 or 2X. Thus, a 200 mm lens
becomes equivalent to a 400 mm lens. These
reduce the maximum aperture of the lens by
one or two f-stops. Caution: Only use a telecon-
verter recommended by the lens manufacturer.
Teleconverters usually do not work well with
wide-angle or zoom lenses., because of the large
number of elements in these lenses.
Zoom Lens
A zoom lens is like many different lenses
in one, because the focal length is adjust-
able. See Figure 3-39. Such lenses are found
in many different focal length ranges. There
are wide-angle zooms, telephoto zooms, and
wide angle to telephoto zooms. Most zoom
lenses have smaller maximum apertures than
fi xed focal length lenses. This means that a
slower shutter speed is needed. Focusing may
also be more diffi cult without autofocus.
28 mm
Wide-angle lens
50 mm
Normal lens
Figure 3-34. A wide-angle lens has a greater angle
of view than a normal lens. A larger area can be
photographed from the same distance.
Figure 3-35. A telephoto lens does for the camera
what a telescope does for the eye. (Sigma)
Telephoto Lens
A telephoto lens acts like a telescope
and makes distant objects appear closer. See
Figure 3-35. A larger focal length gives a
larger magnifi cation. Magnifi cation is mak-
ing things appear bigger than they really are as
seen by the eye. Telephoto lenses are useful for
nature photography, sports photography, and
for taking candid photographs. Figure 3-36
compares wide-angle, normal, and telephoto
lenses.
A large focal length lens can be quite
large and heavy. A compact telephoto lens is
a mirror lens. See Figure 3-37. The light path
is folded by a mirror in the lens, making the
overall physical length much shorter.
Teleconverter Lenses
A teleconverter lens is sometimes also
called an extender. See Figure 3-38. This is a
compact set of lenses that fi ts between the
camera body and main lens. These are a way
to extend the focal length of a lens, usually