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.
Click here for more information about
security cameras lenses.