The starting point of any
C.C.T.V. system is the camera.
Simply stated, a camera is a
light sensitive device that
converts particles of light into
electrical impulses, however,
there is a vast difference in
the quality of cameras available
to the consumer. Factors that
differentiate the various
cameras include whether they are
color, black and white, light
sensitivity, image resolution
and image transfer technology.
The consumer must also consider
the inherent advantages and
disadvantages in each of these
different camera technologies
and decide which features best
fit their individual needs and
goals.
In the past, color cameras have
been both very expensive and
lack-luster in their image
performance, when compared to
black and white cameras. New
technology is now bringing the
innovative technologies closer
together in both the price and
performance scale. The current
differences between the two
technologies are almost entirely
limited to light sensitivity and
light reactivity.
Light sensitivity is measured in
LUX. The lower
the LUX rating, the higher the
sensitivity to light. It is
important to keep in mind that
even the best-rated cameras are
limited by the technology of the
day, as well as the visibility
conditions present at the time
of the surveillance. Although
great advancements in low light
surveillance continue to be
ongoing, the image quality in a
low light situation will rarely
be up to the standards of
daylight surveillance.
Color cameras,
although much more appealing on
the outside when compared to
their black and white
counterparts, generally offer
less low light sensitivity than
a black and white camera. The
other advantage of black and
white cameras over color cameras
is its ability to "see" infrared
light, which is invisible to the
human eye. You can test this by
aiming a standard television
remote at a black and white
camera while watching the
monitor, the flashes you see are
bursts of infrared light. The
advantage of this becomes
apparent in the ability to light
up a dark area with infrared
light, thus making images
visible in almost pure darkness.
With the color camera the area
will appear unlit, however, to a
black and white camera, the area
will appear almost like
daylight.
The black and white camera‚s
reactivity to the invisible
light spectrum can also pose a
disadvantage in certain
applications. Infrared light,
although not visible to the
human eye, is found in abundance
in many everyday situations. For
example, when aiming a black and
white camera at hot pavement, it
will "confuse" the camera
resulting in an unbalanced
image. Professional grade black
and white cameras often
incorporate infrared
cut-filters. These cut-filters
inhibit the infrared light
spectrum in turn decreasing the
cameras low light sensitivity.
The C.C.T.V. Industry measures
image resolution in horizontal
lines. The
higher the line rating, the
clearer the image will appear.
With this fact in mind, consider
that all electronic components
within a C.C.T.V. System, from
the camera, to the VCR, to the
monitor. These items are all
rated in the same way. The
actual resolution of the entire
system will only be as high as
the lowest rated item. For
example, if you have a camera
rated at 450 lines and a monitor
rated at 300 lines, then the
result will be 300 visible lines
of resolution because the
monitor is the lowest rated item
in this example. Another point
to keep in mind is that the line
rating is "Total lines" not
lines per inch. Therefore a 12"
monitor with a 300 line rating
has a far better clarity than a
17" monitor with the same line
rating.
The most recent and predominant
advances in the C.C.T.V.
Industry are the changes in
image transfer technology. This
technology deals with how the
camera takes light particles and
converts them into electronic
images. Without going into too
much detail, image transfer
technologies include the
following:
Phosphorus Tube Cameras
- This camera has low quality,
old technology and is
susceptible to "image burn".
Image burn is when intense light
sources will burn themselves
into the camera‚s light receptor
resulting in the image appearing
"memorized". Although this is
not a problem with modern day
cameras, image burn can still
occur on monitors. Tube cameras
are also known for poor low
light sensitivity.
C.C.D - Also
known as "Chip cameras". This
camera is the most standard of
cameras in the professional
realm. C.C.D. cameras do not
suffer from the problem of image
burn and can incorporate various
methods of signal processing,
which offers a high level of
flexibility to the installer.
CMOS Transfer Cameras
- These cameras are very small
and continue to get smaller as
the technology advances.
Although very attractive in
their size, CMOS cameras
generally do not offer the
signal processing, image quality
or low light sensitivity of the
higher priced C.C.D. camera
models. However, the
technologies are slowly growing
closer together to the point
where CMOS cameras may
eventually take over the
Surveillance Industry.
The Surveillance Industry has
continued to move towards the
implementation of color cameras
that switch to black and white,
or even infrared in low light
conditions. Although there are
some models currently available
on the market, the technology is
not at a point where it is
affordable enough to be
manufactured on a large scale.
