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The advantage to a C-Mount Camera is
that the lens can be changed. If you need to see further
than 35 or 40 ft then you'll need a c-mount camera with
a special lens. C-Mount lenses are available from 4mm to
50mm. A 4mm lens provides facial detail and a 70 degree
angle of view focused up to about 35 ft. An example of
where you might use a fixed 4mm lens is in a small
office, or at home to focus on your driveway. |
A higher millimeter lens will provide further distance, but narrows the field of view. So,a 16mm lens would provide about a 15 to 20 degree angle of view at a focus distance of about 35 ft (or a 70 degree angle of view at about 140 feet). In general, a 8mm lens is like a 4mm lens zoomed in 2 times. Similarily, a 16mm lens is like the 4mm lens zoomed in 4 times.
Many times, the best option is to use a varifocal lens. This will allow you to vary the focus from 5 to 50mm. So when you install the camera you can fine tune the focal distance and angle of view. An example of where you might use a varifocal lens is outside (or inside) a large commercial building where you need more distance than 35 ft. and the varifocal lens will allow you to adjust the focal distance to your preference.
If you want to use cmount cameras outside, you must put them in an outdoor camera housing.
CCTV lenses are available in two different lens mounts. "C-mount" lenses have a flange back distance of 17.5mm; "CS-mount" lenses have a flange back distance of 12.5mm. The flange back distance is the distance from the flange of the lens (beginning of the lens mount) to the focal plane. All of the C-Mount cameras we sell can be adjusted for installation of a CS-Mount lens as well as a C-Mount lens.