190
N. Wiget Lane, Suite 202
Walnut Creek, CA 94598
Phone: (925) 934-CCTV (2288)
Toll Free: (877) 474-CCTV (2288)
Fax: (925) 943-CCTV (2288)
E-mail: info@psscctv.com
Click
here for more information about security
cameras lenses
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.
|
