Understanding
Digital Security Cameras & Security Systems
Camera selection is an important part of your
system. It is the eyes into what is being monitored.
There is a camera for just about every situation
you can think. Let’s start with camera
basics. Almost all cameras purchased now days
are digital verses analog. A digital camera
focuses light from a lens onto a computer chip
that is sensitive to light. There are two types
of chips CMOS and CCD. CMOS has fewer light
receptors than CCD chips. Less expensive cameras
use CMOS chips. High-resolution cameras use
CCD chips. All POM Technologies cameras are
CCD cameras.
How important is the resolution?
That depends on what you are using the camera
for. If you want to see fine details such as
facial features or images on a cash register
display then a CCD camera is a must. In general
expect that a black and white CCD camera will
start at $125 retail including a lens on the
CCD camera body. Everything below that price
is likely to be a CMOS-based camera. CMOS chips
are used in low-end products such as web cameras
you can attach to your PC. They provide a good
picture for relatively short distances (up to
15 feet) and good light levels (all interior
lights on).
If you are using the cameras for commercial
security (like watching for theft) then a CCD
camera is a must.
After resolution the type of lens you use is
an important choice. Two important factors affect
how well the lens works; the iris and lens diameter.
Iris.
An iris controls the amount of light that passes
through the lens opening. Auto-irises adjust
the opening based on changes of light in a room.
This is similar to the human eye. An auto-iris
is very important in areas where the lighting
changes such as rooms with exterior windows
or rooms with variable lighting.
Lens Diameter.
The lens’s opening size (its diameter)
affects how wide and long the field of focus
is. Diameter is represented in millimeters (mm).
The larger the diameter the narrow the field
but the longer it is. So you want a lens with
a low diameter (such as 2.6 mm) for a room about
40 by 40. But a large diameter (such as 8 mm)
would be great for focusing on a distant door.
Low-end cameras come with integrated lenses
that have both a fixed iris and a fixed diameter.
Higher-end cameras have separate lenses that
must be purchased or variable lenses.
Digital Security Camera Types
- Black and white security cameras.
Inexpensive cameras that work well
in high and low light conditions.
- Color security cameras. Inexpensive
cameras that work in general working light.
- Covert security cameras. These
cameras are so small they cannot be easily
seen or are disguised as a different device
(such as smoke detector, clock or teddy bear).
They have a short distance of focus and poorer
resolution.
- Day/Night security cameras.
These cameras switch from color to black and
white depending on lighting levels. They are
ideal for variable lighting conditions.
- High-resolution security cameras.
These cameras have extra light sensors on
their digital chips. They increase the effective
image quality. This type of camera is only
effective with high-resolution monitors.
- Infrared security cameras. These
cameras have their own light source in a light
spectrum that can’t be seen by the naked
eye. These cameras are ideal for small areas
with no light.
- Outdoor security cameras.
These cameras have hardened, waterproof outer
bodies.
- Pan, Tilt, Zoom security cameras.
These cameras allow for remote control of
what the camera is pointed at and what it
is focused on.
- Vandal Proof security cameras.
These cameras come in hardened cases
that can resist the toughest physical abuse.
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