What Good is it?
Advances in CCTV technology are turning
video surveillance into one of the most valuable loss prevention,
safety/security and management tools available today. Retailers use CCTV
to monitor for shoplifters and dishonest employees, compile recorded
evidence against bogus accident claims and monitor merchandising
displays in stores that may be hundreds of miles away. Manufacturers,
governments, hospitals and universities use CCTV to identify visitors
and employees, monitor hazardous work areas, thwart theft and ensure the
security of their premises and parking facilities. New opportunities for
CCTV are growing as fast as the technology and security environments are
||Observe and record theft or
violence by overtly monitoring retail floor space, office
buildings, building perimeters, warehouses, loading docks, and
||Monitor sensitive areas, where
infrequent activities, occur (i.e. confidential records, safes,
||Monitor point-of-sale exceptions
(cash register voids, over-rings, ect.) to reduce cashier theft
||Observe and record shoplifting
||"Walk a beat" by programming a
moving camera to pan, tilt, and zoom within a defined pattern
||Perform covert surveillance
(where legally applicable)
||Integrate with access control
systems to provide video of persons entering and leaving the
||Complement asset tracking
systems to provide video when a tagged asset leaves the premises
||Allow operators to see into
areas where the environment is hazardous to life or health (i.e.
hazardous materials, chemical toxins, ect.)
||Monitor potential accident areas
||Monitor residence halls, common
areas, or high-risk areas to ensure safety of an educational
institution's students and faculty
||Help reduce the severity of some
incidents by the timely dispatch of security, police, fire and
emergency medical personnel.
||Train employees, check stock on
store shelves and monitor retail sales floor coverage,
production lines, ect.
||Demonstrate management's due
diligence towards protecting employees, clients, and visitors,
and perhaps avert or minimize litigation and negative publicity
||Document video images on
magnetic tape or optical hard discs to record events. This
information may be reviewed and later presented as evidence for
prosecution of criminals, or as a training tool
When integrated with access control,
asset tracking, fire systems and other life safety and security
measures, CCTV's "silent witness" provides an additional advantage: the
ability to see and review the impact of these systems on people and
LETS GET STARTED
Many elements must be considered when
designing/installing a CCTV system.
1) Scene & Lighting
2) The Camera
3) The Lens
4) Video Transmissions Methods
5) The Monitor
6) Peripheral Equipment
Scene and Lighting
The scene refers to the objects or area
to be observed and the total environment in which they exist.
A scene often contains different colors, surfaces and materials that
reflect varying levels of light. To select proper equipment, it is
necessary to determine the minimum lighting level (day or night) that
will arrive from the scene to the camera lens. The "available" light
will affect everything from picture clarity to focus (see figure 1).
A scene or target area can be illuminated by natural or artificial light
sources. Natural sources include the sun, the moon and stars. Artificial
sources include incandescent, sodium, fluorescent, infrared, and other
man-made lights. An axiom in CCTV security applications is: The better
the light, the better the picture.
Figure 1: Cameras respond the amount of light reflected from the
Color vs. Black
Color cameras generally require a higher level of lighting than their
monochrome (black & white) counterparts.
Color produces a more natural, richer image than black & white and may
keep the operators' interest for longer periods of time. It also makes
it easier to detect subjects. For example, with a color system a viewer
can easily distinguish a red car from a green one, while on a black &
white system both cars would appear a similar shade of gray. In retail
applications, a color system can help security personnel identify
shoplifters and their clothing more easily and convincingly. Color
accuracy is extremely important in gambling casinos, where hundreds of
dollars can ride on the ability to recognize the difference between a
maroon chip and a red one.
While the use of color cameras is
growing, black & white cameras continue to offer some distinct
advantages. Black & white cameras are better suited for extremely low
The ability to capture good quality images in low light situations
increases the cost of both black & white and color cameras. Before
purchasing cameras, organizations should consider the crossover point
between lighting costs and camera costs. It's possible that low-light
cameras (which are expensive) will cost less than paying to increase the
lighting in a parking lot.
Cameras convert the visible scene
captured by a lens into an electric signal and transmit that signal to a
monitor for viewing.
Several considerations should be taken into account when choosing the
proper camera/lens for any video system:
||The purpose of the video system
(detection, assessment, identification, ect.)
||The overall sensitivity of the
camera needed based upon the actual application
||The amount and varying levels of
light available at the scene
||The environment in which the
camera will operate (indoors/outdoors)
||The field of view (FOV) required
by the application (see figure 3)
Figure 3: Field of view.
Camera performance depends largely upon
the reflected light at the scene and the quality of the cameras imager
(see figure 4).
Where the level of available light can change dramatically, a camera
equipped with automatic iris control can help assure consistent image
quality. Automatic iris control enables cameras to open or close an auto
iris lens to adjust the amount of light passing through the lens. On a
bright, sunny day, for example, an auto iris camera will close the lens'
iris to prevent strong light from reaching the camera's imager. At
night, the camera will open the iris to allow a greater amount of light
into the camera.
Cameras are available in various "formats" expressed as1/2, 1/3, or1/4
inches. These measurements represent the overall usable size of the
camera's imager. In general, you should match the camera's
format to the lens format. For example, a half-inch camera should be
paired with a half-inch lens.
Today, thanks to design improvements, high quality images are possible
with smaller formats.
Figure 4: The imager (or chip).
Fixed and PTZ
CCTV cameras can be fixed or have pan, tilt and zoom (PTZ) capability.
Fixed cameras are mounted on a fixed bracket and cannot move in response
to operator commands. PTZ cameras are motor driven and can pan left and
right, tilt up and down and zoom in and out for close-up or wide-angle
viewing. (See figure 5)
Figure 5: PTZ camera.
A cameras housing protects the camera and
lens from vandalism and the environment. It also can enhance the
appearance of the camera installation and conceal the equipment from
casual observation. All outdoor cameras require a housing of some type.
The National Electrical Manufacturers Association (NEMA) rates housings
on their ability to withstand environmental conditions. Protection from
cold, heat, dust, dirt or other elements is needed to ensure optimum
performance and extend the life of the camera.
Many PTZ cameras today are disguised in dark colored Plexiglas housings
called domes. Dome cameras are found practically every major department
store and in many industrial/commercial locations, hospital, colleges
and government facilities (See figure 6). They are particularly popular
wherever aesthetics are valued.
Dome cameras provide three primary benefits:
||Domes make it virtually
impossible for suspects to determine where the camera is
pointed. Individuals planning to commit criminal activity are
unable to detect whether or not they are under active
||Domes equipped with a camera,
lens, and pan/tilt unit can be augmented with "drones" that have
the same outward appearance, but have no equipment inside. The
result is more apparent camera coverage with a much lower system
||An exposed camera, lens,
pan/tilt unit and associated wires are
unsightly. A dome makes the collection of equipment more
aesthetically acceptable, and does not detract from the interior
design of a retail or business office environment.
Placing a mirrored finished or smoked
bubble around the dome can conceal a dome camera further.
However, when this is done, the bubble has the effect of sunglasses,
reducing the amount of light reaching the lens and affecting the color
accuracy picked up by the camera.
Figure 6: Dome cameras.
The Lens (Optics)
Lenses (Optics) play an important role in
the design of a CCTV system. Their primary function is to collect
reflected light from a scene and focus a clear, sharp image on the
camera's imager. Typically, the more light that passes through a lens,
the better the quality of the picture.
Selection of a lens is especially critical because it directly affects
the size, shape, and sharpness of the image to be displayed on the
imager. Factors such as distance from the scene, focal length, desired
field of view, lighting and format affect the size and clarity of the
image on the camera's imager.
Field of View
The field of view (FOV) is the actual picture size (height and width)
produced by a specific lens. If the field of view is not suitable, you
may consider using a different lens (wide angle, telephoto, etc.) to
increase or decrease the field of view. Tables are available to
calculate the proper imager size, lens and distance combination needed
to produce a desired field of view. See page 92 of this catalog.
Camera lenses can be divided into two basic types: fixed focal and
varifocal (or zoom). A fixed focal lens has a constant focal length,
while a Varifocal lens can change its focal length. Focal length is
simply the distance from the optical center of the lens to a focal point
near the back of the lens. This distance is written on the lens (in
millimeters) and indicates the field of view produced by the lens (See
Figure 7: Focal length.
Fixed focal length lenses are available
in various wide, medium, and narrow fields of view. A lens with a
"normal" focal length (Ex: 8.0mm on a 1/3" camera) produces a picture
that approximates the field of view produced by the human eye. A
wide-angle lens has a short focal length, while a telephoto lens has a
long focal length (See figure 8). When you select a fixed lens for a
particular field of view, bear in mind that if you want to change the
field of view, you must change the lens.
Figure 8: Wide angle vs. telephoto.
When both wide scenes and close-up views
are needed, a varifocal or zoom lens is best. A zoom lens is an assembly
of lens elements that move to change the focal length from a wide angle
to telephoto while maintaining focus on the camera's imager. This
permits you to change the field of view between narrow, medium, and wide
angles, all on one lens.
The ability of a lens to gather light depends on the relationship
between the lens opening (aperture) and the focal length. This
relationship is symbolized by the letter f, which is commonly referred
to as the "F-stop," and can be found printed on the side or front of the
lens (see figure 9). The lower the F-stop number, the larger the maximum
lens aperture and the greater the lens' ability to pass light through to
the camera's imager.
For example, a lens with an F-stop of
f/1.2 can gather a great deal more light than a lens with an F-stop of
f/4.0. A lens with a low F-stop number is called a "fast" lens
Figure 9: The F-stop indicates the lens' light gathering ability.
Depth of Field
Another consideration when determining the proper lens is depth of
field. Depth of field is the area in focus before and behind a subject
(see figure 10). This means that when you focus precisely on a subject,
a certain distance in front of and behind the subject also will be in
focus, although not as sharp. Depth of field increases or decreases
based on the 1.) Length of the lens, 2.) The lens aperture and 3.)
Distance from the camera to the subject.
Figure 10: Depth of field.
Each of the three depth of field
factors will yield the following:
1) Lens length
||Short lens (i.e.
||= longer depth
|Long lens (i.e.
||= shorter depth
||= shorter depth
||= longer depth
3) Distance to subject
||= shorter depth
||= longer depth
Purchasing and planning decisions should
take these factors into account since depth of field can affect image
quality (and may jeopardize the ability to identify and prosecute
subjects). If depth of field is important, you may want to explore
options such as increasing artificial lighting or installing cameras
with normal lenses rather than telephoto lenses, etc.
Camera lenses generally come with either a C-mount or CS-mount and must
be matched appropriately to the camera's mounting requirements. The
difference between the two mounts is the distance of the lens optics
from the camera imager. The C-mount lens is 17.5mm from the imager; the
CS-mount lens is 12.5mm from the imager.
Follow these guidelines when purchasing
||A C-mount lens can be used on a
CS-mount camera only if a 5mm spacer ring is added
||A CS-mount lens cannot be used
on a C-mount camera
The purpose of the transmission medium is
to carry the video signal from the camera to the monitor. Today, many
video transmission methods exist: coaxial cable, fiber optic, phone
lines, microwave, and radio frequency. Due to varying application needs,
it is possible to find several video transmission technologies in use
within the same CCTV system.
The choice of transmission medium depends on factors such as distance,
environment, cost and facility layout. In addition, nearly all methods
of transmission suffer from various forms of interference or loss. The
essence of good design is to minimize this impact. Examples of current
video transmission mediums include:
A coaxial cable is one that provides a continuous physical connection -
or closed circuit - between the camera and the monitor (see figure 11).
The cable is shielded to minimize interference from any nearby
electronic devices or electrical wires. Copper braided coaxial cable is
recommended to maximize conductivity and minimize potential
interference. For traditional CCTV systems, as well as many applications
today, this is the most common and economical method of signal
transmission over relatively short distances.
Figure 11: Coaxial Cable
Fiber optic technology changes an electronic video signal into pulsed or
laser light and injects (transmits) it into one end of a glass rod (the
fiber optic cable). At the other end, a receiver translates the pulsed
light back into an electronic signal capable of being displayed on a
monitor. The transmission is unaffected by any kind of interference,
water in conduit or high voltage being run in the same conduit. Fiber
optic cables have a large signal capacity (bandwidth) and no possibility
of a spark from a broken fiber. Hence, there is no fire hazard to a
facility even in the most flammable environment. Fiber optics offers a
cost-effective method of sending large transmissions over long
A telephone line is a standard twisted pair of wires that can transmit
the image for distances up to one kilometer without video signal
boosting. This dedicated line connects the transmitter (camera end) with
a receiver (monitor end). Through the use of specialized transmission
and receiver equipment, it is possible to use standard telephone lines
for video signal transmission.
If already in place, microwave can be a very efficient and
cost-effective method of delivering black & white or color video.
Microwave turns the video and data signals into high radio frequency
signals and transmits them from one point to another via free air and
space. A receiver then converts the transmission back into the video and
data signals and displays the scene on a monitor. Good quality
transmission can be achieved over a line of sight path (see figure 12).
Microwave technology offers a large bandwidth to carry video, however,
it can be affected by environmental conditions. It is a practical option
when a wire path between the camera and monitor locations cannot be
established or is prohibitively expensive. Microwave transmission is
regulated by the FCC, and a license is required.
Figure 12: Microwave requires a line-of-site transmission.
Radio frequency (RF) is a reliable, but short distance, line-of-sight
video transmission technology. It is becoming increasingly popular where
hardwiring methods are either impossible or impractical, and has been
used successfully to reduce cabling costs even within large buildings.
Environmental conditions or other RF in the area can affect it.
The monitor receives the transmitted
electronic video signal from the camera and paints it across a cathode
ray tube (CRT) to display an image to a viewer. Although similar in
function to a TV set, a CCTV monitor provides higher lines of resolution
(better picture quality) and accepts only video signals rather than RF/antenna
Lines of resolution refers to the total number of horizontal lines the
camera or monitor is able to reproduce. The more lines on a screen, the
better or sharper the video picture will appear. CCTV monitors can
provide up to 1000 lines of resolution compared to an average of 300
lines provided by television sets.
Figure 13: Nine and fourteen inch monitors often serve as
dedicated monitors. The 14-inch
size is also popular for call-up monitors. Monitor size is measured
Several factors can affect the monitoring
function: Size of the monitor (9" and 14" are popular sizes), its
positioning and angle relative to where the viewer sits, the quantity of
monitors, and the quality (resolution) of the monitor itself (see figure
13). In all cases, sufficient growth must be factored into any console
design. It's also important to note that all monitors generate heat.
Whether on a table or enclosed in a console, be sure to provide adequate
ventilation and air-conditioning.
Most CCTV systems use both dedicated monitors and call-up, or
Switchable, monitors. A dedicated monitor displays the video from only
one camera. A call-up, or Switchable, monitor enables operators to "call
or switch" different cameras to the monitor. Generally,
call-up/Switchable monitors are larger than dedicated monitors and give
operators the ability to view multiple images simultaneously
(multiplexed) as well as scrutinize the camera image more closely.
There are many different monitor sizes available. When choosing the
proper size of monitor, you must first determine the distance of the
monitor in relationship to the user. Also determine the quantity of
cameras to be displayed on a given monitor simultaneously (multiplexed).
The Peripheral Equipment
As the number of cameras and
monitors increase, simple system designs eventually give way to more
complex designs that require peripheral components. These peripheral
components may include switchers, VCRs, multiplexers, quad splitters,
video printers and time date generators.
A video switcher enables different cameras to be switched to different
call-up monitors. In a smaller, cost-conscious application, a manual
switcher allows users to select the camera they want to see by pressing
a button associated with the camera (see figure 14).
Figure 14: A switcher makes it possible to switch cameras on a
popular type of switcher, a sequential switcher, contains circuitry that
will switch one camera to another automatically. The operator can set
the length of time (dwell time) that a scene remains on the monitor
before sequencing automatically to the next camera. This allows
operators to keep tabs on numerous cameras with only one monitor, but
also creates a drawback known as "switcher dilemma."
To illustrate switcher dilemma, imagine a system with eight cameras,
each programmed to switch after "dwelling" on the monitor for five
seconds. In this scenario, a considerable gap will occur between the
time the first image is displayed and the time the eighth image is
displayed. If the dwell time is shortened, operators may not be able to
assimilate each camera image before it switches. The situation worsens
when recording the video for review at a later time. On playback, you
may see a door opening on camera 1, then suddenly see the video switch
to camera 2, followed by camera 3, camera 4, and so on. By the time
camera 1 appears again, the door is closed, and you are left wondering
who came through the door while cameras 2 through 8 were flashing
sequentially on the monitor.
Switcher dilemma can be solved with more sophisticated switchers, more
operators or an alarm feature that will display video image
automatically when an alarm point is activated.
A matrix switcher is a more complex design enabling the user to switch
any video signal to any call-up monitor in a large-scale system. They
normally incorporate P/T/Z control and other features such as presets
and alarm inputs/outputs.
Unlike conventional recording systems, a video multiplexer collects
full-screen pictures from up to 16 cameras and displays them
simultaneously on a monitor (see figure 15).
Operators have the option of displaying any camera full-screen or
multiple cameras in reduced size.
Figure 15: A 16-position multiplexer currently displaying only 7
Multiplexers also can record all cameras
in the system onto a single videotape. The cameras are recorded
sequentially at a high rate of speed. As mentioned earlier, a standard
video signal is comprised of 30 separate frames each second. In a video
system containing 15 cameras, the multiplexer selects two frames from
each camera and records them to a single videotape. The result is an
effective frame rate of 2 frames per second, instead of the standard 30.
Most multiplexers today contain a motion detection feature that enables
the system to record more frames of video from cameras showing motion
than from those not showing any motion. The multiplexer does this by
reallocating frames from one camera to another as needed. The net result
is higher quality recordings of scenes that are more likely to be
important to security personnel.
When a time lapse VCR is used with a multiplexer, the recording mode
should be as short as possible to reduce the number of seconds required
to record all cameras (remember, cameras are recorded sequentially) (see
This is why it is a great advantage to use hi-density or virtual
real-time TLR's when using multiplexers. Virtual real-time VCRs record 4
times the frames per second of conventional time-lapse VCRs.
Figure 16: The VCR, working with a multiplexer and several
records fewer frames per second in time-lapse mode.
One of the strongest advantages of using
multiplexers is that during playback, the multiplexer decodes the tape
allowing investigators to display only selected frames with the same
address. This pullout feature saves investigators hours of time
reviewing recorded actions. Another advantage is that during playback,
any desired camera can be displayed full-screen.
Multiplexers offer system administrators an
effective means of managing multi-camera surveillance systems:
||With the high-speed switching
technique, multiplexers offer maximum coverage of all cameras
without the gaps created by sequential switchers
||Multiplexers may be able to
reduce CCTV costs by reducing the number of monitors, VCRs, and
||The number of tapes needed for
video storage may be reduced
||Savings in space, heat, power,
and ventilation also may be possible
The main feature of a quad splitter is the ability to compress images
from four separate cameras and simultaneously display them on a single
monitor screen (see figure 17). When four cameras are displayed, each
occupies a quarter of the screen. A single camera can be selected and
displayed full-screen, as well.
Unlike multiplexer recording, quad
splitter recording yields only what appears on the monitor screen. If
the VCR is recording a four-camera display, then playback will show four
Figure 17: Quad splitters can display four cameras on one
Most CCTV systems use VCRs to record video images from the dedicated
and/or call-up/switchable monitors (see figure 18). Recordings make it
possible to view events that may have gone unnoticed at the time they
occurred or that may require close scrutiny later. Technological
advances now make it possible to record images in digital form on a
computer disk. While this technology shows great promise for the near
future, VCRs presently are the most prevalent recording method.
Figure 18. A simple CCTV system with VCR
VCRs designed for CCTV can record video
images in either real-time or time-lapse modes. In the real-time
recording mode, the tape moves at the same speed as home VCRs (2 to 6
hours) and captures 30 pictures per second. This produces high quality
recordings, but requires operators to change tapes every two to six
hours. The 24-hour real time VCR will record 24 hours of video on a
single tape at 20 pictures per second.
It is considered a real time recorder because 20 pictures per second
approximates the ability of the human eye to easily distinguish moving
Time-lapse recording makes it possible to
record video over long periods of time on a relatively small amount of
videotape. Time-lapse recording can capture from 12 to 960 hours of
video on one T-120 tape. However, the number of pictures recorded per
second in time-lapse mode decreases significantly as the recording time
increases. As fewer pictures are recorded per second, critical images
may not appear on tape, and movement (e.g. a car traveling across a
parking lot) may appear jerky (see figure 19).
Figure 19: Fewer pictures are recorded when using time-lapse
mode, causing motion to
appear jerky. Notice how cars "disappear" when fewer frames per second
seconds per picture and number of pictures per second rendered by
various time- lapse VCR recording modes are shown in the next table:
Another way to capture video on tape is
through alarm recording. With this method, the VCR usually runs in
time-lapse mode until an alarm occurs. The VCR then switches from
time-lapse mode to real time mode, capturing video images at a rate of
30 pictures per second. After the alarm resets, the VCR returns to
time-lapse mode to conserve tape. The CCTV system will need an alarm
switching mechanism in order to perform this function.
When a time-lapse recording is played back at normal playback speed, the
playback will present events at a speed faster than real time. It is
common to play back a time-lapse recording in real time mode to speed
the time necessary to review the tape. If necessary, the tape can be
slowed to review those events that require greater attention.
A more recently developed method of recording video images is that of
Digital Recording (see figure 20).
Figure 20: A Basic Digital Recorder System.
Digital recorders compress and store
images to a computer hard drive using various compression techniques.
These techniques include JPEG, MPEG, Wavelet and a host of other
proprietary methods. Images can be stored at a rate of 20 frames per
second (fps) to as many as 480fps depending on the software features
offered by the manufacturer.
Operating systems offered by manufacturers vary from Linux to Unix to
Windows based systems. Although Windows is the most user friendly and
familiar system, it tends to be less stable than it's lesser-known
Archived recording time varies depending on the size hard drive in the
recorder. Hard drive sizes range from 0 (external only) to 400gb
internally with option of raid storage for virtually infinite capacity.
Hard drive size should be considered conjunctively with the time period
necessary to archive.
Many Digital Recorders incorporate multiplexing with inputs varying from
4, 9, 16 and as many as 32 inputs. Similar to the conventional
multiplexer/VCR setup, the frame rate will be divided among the cameras
being recorded. However, unlike conventional methods, each camera input
of a digital recorder can be programmed to record more or less frames
per second depending on camera priority (Ex: camera #1 = 10fps, camera #
2 = 5fps, camera # 3 = 12fps, camera # 4 = 3fps using a 4 input recorder
with maximum 30fps).
Another very distinct advantage to digital recording is the ease of
locating events. No more fast- forward and rewind. Just type in a time,
date and camera number and you can playback instant images.
Other options available with DVRs include motion detection, remote
viewing via LAN, WAN, or Internet, on board media such as CD Rom, DAT
storage or removable hard drives, SCSI and USB ports as well as remote
control of pan-tilt devices and the list grows everyday!
Work with your Concord Camera Systems sales representative to determine
which digital product is best for your application.
A video printer (see figure 21) produces a hard copy printout of any
live or recorded video scene, using thermal or other sensitized paper.
The "still" photo can be used for multiple purposes, such as providing
suspect identification to police agencies, alerting employees to safety
hazards, etc. Photo printers are available in black & white or color.
Figure 21: A photo printer.
Time Date Generator (TDG)
A Time and Date Generator can annotate the video scene with
chronological information. Also, a camera identifier is placed on the
monitor screen to identify the camera scene being displayed. Today, most
VCRs, multiplexers and camera controllers have this function built into