47
Chapter 3 Lenses
Figure 3-38. A teleconverter can increase the focal
length of a lens by a factor usually of 1.4X or 2X.
(Sigma)
Figure 3-39. A zoom lens can take the place of a number of fi xed angle lenses. A. This autofocus lens covers
the wide angle range of 12–24 mm. (Sigma) B. This autofocus lens covers a wide angle to telephoto range of
18–200 mm. (Nikon) C. This large telephoto lens covers the telephotos ranges of 200–400 mm. (Nikon). When
used with a digital camera having an equivalency factor of 1.5X, what are the actual ranges compared to a
35 mm camera?
by twisting a ring to focus and pushing or
pulling the ring to change focal length, or
zoom. A two-touch zoom lens has two rings,
one for adjusting focus and the second for
changing the focal length.
Care of Lenses
Never clean a lens with facial or toilet tis-
sue, silicon eyeglass cleaning tissues, handker-
chiefs, fi ngers, or water. For best results, use
the following procedure to clean a camera
lens thoroughly and safely.
C
B A
Manual-focusing zoom lenses are either
single-touch or two-touch. With a single-
touch zoom lens, focusing is accomplished