 No matter how good or expensive a camera may be, it is useless
without the proper lens. For most applications, a fixed-focus lens is adequate. Fixed
focus lenses have fixed field of view and are the cheapest in the family of lenses.
Commonly used focal lens vary from 4.0 mm (wide angle) to 1000 mm (tele-photo) The 4.0 mm
lens has a wide horizontal view. Long focal length lenses are generally used outdoors,
viewing remote areas, and usually are quite large and require very stable mounts (or
pan-tilt drives) to obtain good quality pictures.
 The zoom
lenses are used particularly in remote monitoring applications, mostly with pan-tilt where
the Field of view (FOV) seen by the lens and camera must be varied from wide angle to
narrow angle and vice versa. The zoom lens permits viewing narrow, medium and wide angle
scenes depending on its setting thereby permitting initial wide field viewing of an area
and then close-in tele-photo viewing of one portion of the area. These lenses are
available for either manual or motorized operation.
Pin Hole cameras do not use a lens and normally their quality off picture is inferior as
compared to lens based camera but still of acceptable quality for most of usual
applications.
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