Outdoor Lighting for Video Surveillance

This Application Note describes the most popular outdoor lighting sources, their relative value in scene lighting for video surveillance cameras, and basic recommendations for cities and agencies considering installing new lights, replacing lights, installing new public area surveillance cameras, or upgrading existing surveillance systems.

Light Sources

The best light source for video cameras are the "white light" sources that look good to the human eye. The best two are tungsten-halogen (also called halogen, quartz-halogen or quartz-iodine lamps) and metal-halide. Both of these light sources are becoming increasingly common in both outdoor commercial and public applications.

Traditional incandescent, such as "flood" lights and many types of stadium lighting, also produce excellent quality light for video cameras. Traditional incandescent fixtures are lower cost than tungsten-halogen and metal-halide. However, they are less efficient, and so use more electricity for the same amount of light output. Typically, permanent installations costs, such as poles, wiring, labor and expected electrical costs are far higher than the cost of the fixtures. Therefore, most public agencies find the more efficient lamp types are more cost-effective. Also, tungsten-halogen and metal-halide lamps generally last longer than tungsten incandescent lamps.

The most common outdoor lamps are low-pressure sodium (deep orange light) and high-pressure sodium (yellowish light). Many streetlights are high-pressure sodium. Although these are adequate for most general security and night lighting applications, their narrow frequency light is very poor for most video cameras. True monochrome cameras tend to be most tolerant type of camera for this type of narrow-spectrum light. However, that does not mean that video from a monochrome camera monitoring a scene illuminated by sodium lighting will necessary be adequate to the intended application. This caution is still accurate, even if the camera is rated for "night" use and has an excellent low-light specification.

Mercury-vapor lamps typically produce a blue-white light. This is an older technology that is not commonly used for new lighting. The performance of this light with video cameras is between that of sodium lamps and incandescent lamps. This lamp type is not generally recommended for new applications involving video cameras. Mercury-vapor lamps are often found in parking lots and on building fascias.

Fluorescent lighting usually produces adequate video images, if the light is sufficient;y bright. Fluorescent lights are most commonly long, inexpensive tubes. They are found in the interiors of most office buildings, and are commonly used in parking garages. However, the response of cameras to fluorescent light is not completely predictable. This light source produces a high-frequency (120 Hz) flicker. Each color phosphor in the tube that makes the light appear white to humans has a different response time. Thus, camera response can vary significantly by camera type, camera settings, and even the brand of bulb. Often, existing outdoor fluorescent lighting is insufficiently bright for good quality video.

Compact-fluorescent bulbs (coiled tubes with a standard screw base) are being used increasingly in residential and apartment building walkway lighting. This type of lighting has better consistency than traditional fluorescent bulbs. However, installed compact-fluorescent lighting is rarely bright enough for acceptable video. A 23-watt compact-fluorescent lamp produces (when new and warmed up for five minutes) the same amount of light as a 100-watt standard light bulb. Some fixtures can be upgraded to use 75-watt compact-fluorescent bulbs.

Infrared lighting is commonly used for covert nighttime video surveillance. Traditionally, these special-use spotlights used incandescent or metal-halide lamps with filters to remove the visible light. Increasingly, infrared lamps consisting of LED arrays are replacing the earlier, hot, sources. Video sensors used inside of video cameras are sensitive to infrared light beyond the range of human eyes. This is true both for older analog cameras and the newer digital cameras. It is true for tube-based sensors, CCD sensors, and CMOS sensors. Both the camera and lens have to be designed for infrared use for this capability to be effective, however.

Infrared sources are often rated by wavelength. Common numbers are 850 nm, 880 nm and 950 nm, although other frequencies ratings are also used. nm is nanometers. 850 nm and 880 nm are visible to humans as deep red. 940 nm and longer wavelengths are completely invisible to humans. For completely covert operation, or for use in complete darkness, 940 nm or longer light sources should be used. The deep red of the cheaper, brighter, and more common 850 nm sources may be disguised in some covert applications by collocating the infrared lamp with a bright, point-source white light. Infrared light sources must be paired with infrared capable cameras. Most infrared lights sources are narrow angle. Applications are most common for well-defined, small-area locations, such as a gate, doorway, alley, or in front of an elevator.

Flash lamps are used in specific, motion-triggered applications, such as at red-light cameras (RLC) at intersections, and at tollbooths. Cameras are normally still-image cameras. Such specific purpose flash lamp based applications usually produce excellent results. In these applications, the lighting, camera, and software are an integrated product.

True thermal cameras use no light source at all. They respond directly to the heat emitted by mammals (including humans) and vehicles. These cameras are currently expensive but have found excellent applications in reservoir monitoring, bridge and waterway monitoring, and for airport perimeter surveillance.

Other Issues

Both mercury-vapor lamps and metal-halide lamps can cause eye and skin injuries if the fixtures are damaged or broken. This is because the fixtures typically provide a UV blocking filter that removes the dangerous UV radiation the lamps emit. These lamp types should only be used in applications where regular, enforced inspection is possible.

The above two light sources have a turn-on time. This can vary from about two seconds to five minutes. For applications where the light is on for hours, this warm-up time is rarely a problem. For applications using motion sensors, or emergency power, or for portable applications, the warm-up time may be a minor annoyance, a major problem, or may be entirely unacceptable.

Motion Detection

The use of infrared-sensitive motion detectors to trigger lighting has several advantages:

• It enables the use of brighter and lower cost lamps.
• The triggered light may be bright enough for high-quality video capture.
• It may provide a deterrent effect, due to the "surprise" of the light coming on.

The use of motion-triggered lighting is far more common in Europe than in the United States. Typical applications include hotel hallways and parking lots.

Commercial-grade motion sensors are both low cost and reliable. However, these installations have drawbacks.

• Delay or failure to turn on light may cause an injury, producing a liability. Such concern may not be applicable in places where there was little or no previous light, but in the US, this is a common concern.
• False triggers due to nocturnal animals, reflected headlight beams, legitimate human activity or wind. Wind causes false triggers by moving foliage, window panes or the camera mount.
• Frequent triggers (real or false) can shorten the life of some lamps types.
• Slow-turn-on lighting can permit a suspect to escape or move too fast to be captured on video.
• Fast-turn-on lighting can blind a video camera for several seconds, allowing a suspect to escape prior to video capture.
• Repeat criminal activity will simply move out of range or into shadows. For public property, moving the crime a block away has minimal value. However, for a private property owner, or a school, this may be an acceptable alternative.

A current trend is to purchase digital video cameras or system software that uses the camera's digital video data plus CPU processing to detect motion. This detection is usually used to trigger digital recording and/or increased frame-capture rate. It may also produce an external alarm trigger and/or turn on additional lighting. Such software-detected motion-detection is becoming the industry standard. This system has several advantages:

• No additional hardware is required.
• The software may be free, as it may be included with a camera or with a software package.
• Frame masking and adjustable sensitivity can be used to significantly reduce the number of false triggers.
• For most applications, locating key recorded events is much faster with this technology.
• In most applications it is effective.

Software based motion-detection also has challenges:

• The night-scene must be illuminated for software-based motion detection to work.
• Setup and maintenance requires an expert.
• The best systems, sometimes called "intelligent video," are expensive.
• Unless a scene is brightly illuminated, the "noise" of night-vision cameras will typically cause a large false-trigger rate.
• Even light wind will often cause an annoying false-trigger rate.

Despite the implementation challenges, video surveillance systems that incorporate some type of motion detection and some type of dynamic lighting are often the most effective systems both for deterrent and for court-acceptable evidence capture of criminal activity.

Portable and Mobile Applications

Implementation and use of portable video surveillance depends heavily on the application. For events such as concerts or street fairs, the system need not (and perhaps should not be) covert at all. Standard rental lighting may be used.

If the goal is to capture specific, repeat criminal activity, the system must be fully covert.

If the goal is to stop or discourage specific, repeat criminal activity, then the implementing agency must consider to where that criminal might relocate.

Mobile and covert surveillance systems are among the most effective of all video surveillance installations. "Going to where the problem is," has obvious applicability to many types of problems.

Temporary and covert lighting does not necessarily have to be co-located with the temporary or covert camera. Bright, temporary video lighting may be disguised as work-lights for another activity, such as street or grounds maintenance. Bright lighting, alone, if the criminal does not believe enforcement personnel are watching him, may not discourage criminal activity.

The electricity cost for temporary, bright surveillance lighting is usually acceptable compared with the other costs associated with deploying a mobile surveillance system, and compared with the savings of prevented criminal activity.

Implementation Recommendations

There are few simple answers for nighttime surveillance lighting. Complex, overlapping issues include equipment costs, deployment cost, operating costs, community acceptability, compliance with legal requirements, purpose, potential gain, and effectiveness.

Most communities and public agencies should first consider a trial system before they install multiple cameras at multiple sites. The trial system should be similar to, or identical to the larger expected system, both in terms of the site and the equipment.

"Phased" digital video surveillance system installation is typically considered a best practice for government agencies.

It may be advantageous to employ a consultant or a vendor to review the requirements, and write a system specification prior to deployment. However, night-vision application requirements are so unique and the hardware available is so varied that the public agency should seriously consider, with or without a consultant, a pilot system.

In addition, the agency should budget time and money for system tuning and adjustment, which might include swapping out cameras or light sources.

Hardware and software specifications for night-visions video surveillance are frustratingly inadequate to predict system performance. For example, two cameras may have identical low-light sensitivity (for example, 0.003 lux) yet produce dramatically different quality video. Two light sources may be rated the same wattage and the same frequency, yet one will produce far better video results than the other. Two infra-red motion detectors may be specified to work at the same range, yet one is much faster responding than another, or one is much better at rejecting false triggers.

Wind, distant automobile headlights, animals, and other false trigger sources can be difficult to predict in advance. Consultants maybe surprised (and uninformed about) how much legitimate traffic there is in a "closed" area.

Criminals can be remarkably adept at learning work-arounds to technology that interferes with their intentions. For example, case studies show criminals timing their motion synchronized with "automatically panning" cameras to stay entirely out of the camera's moving field of view. Some criminals have learned to move so slowly that they will not trigger motion sensitive detectors. However, the most common response of street crime to visible cameras is to ignore them. Too often, in the past, poor quality analogy cameras or broken systems meant that even if their crime was captured on videotape, there was no evidence usable for arrest or prosecution.

Often, the most effective applications of outdoor night-vision video surveillance are to keep "closed" areas actually closed. Such areas include skate parks, maintenance yards, vehicle storage yards, school property, small parks with curfews, campus interiors, and controlled-access parking garages. What this means is that the digital video surveillance system detects activity that is not permitted based on time and location. The system sends an immediate alert to an operator who immediately views the video. If appropriate, an officer is then quickly dispatched to remove the offending individuals from the closed area, typically with a warning, before a serious crime is committed. This approach has a high level of effectiveness.

Other points to note:

• All "high risk" facilities benefit from quality video surveillance systems as part of overall security procedures.
• Flexibility and responsiveness is the key to successful implementation of night-vision video surveillance systems.
• Vandalism and auto-related crime rates are those that have been shown, in controlled studies, to be most affected by the installation of video-surveillance.
• Depending on the jurisdiction, simply moving the criminal activity into another jurisdiction may be sufficient justification for installing a system.

Future Improvements

We can expect to see closer integration of lighting sources, motion detection, cameras and software.

For gang-related activity, injunctions against gang members conducting gang activities in a specified area can be effective in crime-reduction. See our White Paper, "Networked Video Surveillance and Gangs." Networked video surveillance plays a crucial role in gang injunctions by providing an effective means of enforcement.

As the industry moves rapidly towards the adoption of IP-based systems, extensive use of wireless technology, and the expanded use of intelligent video, we can expect continued dramatic improvements in the effectiveness and deployment rates of these video surveillance technologies.

About SightMind, Inc.

SightMind is a national company dedicated to providing IP-based video surveillance (IPVS) solutions to schools, government agencies, and commercial/industrial facilities.
SightMind was founded with the goal to bring highly reliable IP-based video surveillance systems to the major institutions and organizations in North America, including high schools, colleges, natural resources, utilities, transportation, public safety, shopping centers, industrial facilities, and large private sites. Legacy CCTV systems are being replaced and updated with modern, digital, networked systems. These IP-based systems provide extensive benefits to their owners, including expanded storage, higher reliability, high resolution sufficient to provide clear identification of people and vehicles, easier administration, cost savings, and customer service benefits far beyond the original security motivations.

IP-based video surveillance systems provide not only proven security benefits, but also site operational cost savings, labor savings, and customer service benefits beyond most customer's original expectations.

www.sightmind.com
SightMind, Inc., 48025 Fremont Blvd, Fremont, CA 94538
Tel 877-478-7988
email: info@sightmind.com