43
Chapter 3 Lenses
in the camera body. These are found mainly
in older cameras. Caution: Do not force a screw-
mounted lens if it does not turn easily in the cam-
era body. Forcing may damage both the lens and
camera body, thus resulting in costly repairs.
The bayonet lens mount fi ts into a mount-
ing fl ange on the camera body. A twist of 90°
or less locks the lens into place. Nearly all
major manufacturers of cameras with lenses
that can be changed use this mount. See
Figure 3-30.
Lens Scales
Adjustable lenses usually have three
scales printed on them:
• Distance scale. This tells the operator how
far away the subject is when the subject is
in focus.
• Depth of fi eld scale. It indicates the
nearest and farthest distances the subjects
in the picture are in sharp focus.
Figure 3-28. A large f-number indicates a small aperture. Stopping down means reducing the size of the aperture.
Figure 3-29. Screw type lens mounts were once
very popular.
Figure 3-30. Bayonet type lens mount. Modern SLR
cameras use this type.