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The field of view can be classified into three types:
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Normal view:
offering the same field of view as the human eye.
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Telephoto:
a narrower field of view, providing, in general, finer details than a human eye can
deliver. A telephoto lens is used when the surveillance object is either small or located far
away from the camera. A telephoto lens generally has less light gathering capability than a
normal lens.
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Wide angle:
a larger field of view with less detail than in normal view. A wide-angle lens
generally provides good depth of field and fair, low-light performance. Wide-angle lenses
sometimes produce geometrical distortions such as the “fish-eye” effect.
Figure 3.2a Different fields of view: wide-angle view (at left); normal view (middle); telephoto (at right).
Figure 3.2b Network camera lenses with different focal lengths: wide-angle (at left); normal (middle); telephoto (at
right).
There are three main types of lenses:
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Fixed lens:
Such a lens offers a focal length that is fixed; that is, only one field of view
(either normal, telephoto or wide angle). A common focal length of a fixed network camera
lens is 4 mm.
CAMERA ELEMENTS - CHAPTER 3
