Lighting Up the Scene for Effective Video Surveillance
a&s International | Date:
Special considerations must be given to lighting when designing a video surveillance system. Existing lighting conditions at the site often need to be compensated for, may it be brightness, darkness, contrast or a mixture. Sites with complex lighting conditions can be challenging to tackle.
While megapixel cameras are catching up fast, analog cameras still perform better under very difficult lighting conditions in most cases, said Kostas Mellos, Commercial Leader for Video and Transmission, Interlogix (a UTC Fire & Security Company). “For example, if you have a camera inside a building looking out towards the lobby where sunlight is reflected on the glass or floor, megapixel cameras will generally have a hard time dealing with that. An analog camera with backlight compensation will cope with this scene a lot better.”
Network cameras need lighting to produce high-quality images at night, reduce their bandwidth and storage requirements, and allow faster frame rates, said David Lambert, Sales and Marketing Director for Raytec. “Without good lighting, network cameras won't live up to their full potential; they won't be able to deliver the superior resolutions they are capable of, and may overload a system with large amounts of data.” Appropriate lighting significantly reduces noise in the picture and increases the efficiency of video compression and transmission.
As every project is different, specific lighting needs to be accounted for. “This can range from invisible IR lighting for video surveillance cameras to monitor a scene covertly, visible white light to connect with detector technology for deterrent purposes, marine-grade lighting for hazardous environments and PoE lighting, to white light for general illumination purposes concerned with lighting areas for pedestrians and not just cameras,” Lambert said.
Many projects such as hospitals and schools use traditional street lighting, as opposed to dedicated lighting for security and surveillance purposes, to make the area look safer and to capture color images, Lambert continued. “However, old-style sodium street lighting has a poor color rendition with a dull yellow glow that is no good for capturing high-quality, detailed images. It is also typically slow to start and cannot be used for deterrent purposes. In projects which require lighting over a large area, such as fence lines or parking lots, sodium lighting can't perform, delivering uneven lighting and leaving many areas unlit and unsafe.” A lighting solution capable of delivering an even spread of illumination with true color rendition drastically improves performance for video surveillance systems.
With IR and white-light illuminators for surveillance purposes, a camera looking out across a scene on a vertical plane to monitor a subject requires more straightforward considerations: distance and angle, typically up to 1000 meters with only two lighting units, with angles from 10 to 120 degrees, Lambert said.
With white light for general-area illumination, which is typically used for lighting down onto a scene across a horizontal plane where a camera is not concerned, it is a little more complex. According to Lambert, typical considerations include:
1. What is the purpose/application? This typically identifies how much where it needs to be directed, its mounting height and so on. For example, large parking areas, long narrow pathways or aesthetic building decorations are all different.
2. Are there any specific lighting requirements set out by customer site plans or application standards? Considerations include average illuminance, minimum illuminance, uniformity (minimum versus average), diversity (minimum versus maximum) and horizontal or vertical plane.
3. Are there any other site specifics? Is a site plan available? Mounting height is critical, as well as information regarding any obstacles, hills, trees fence lines or walls that will affect the lighting. Does the lighting need to be fitted to existing lighting columns?
It is crucial to specify the best lighting that fits the project requirements. Key considerations are distance, angle, maximum consumption, input power, maintenance factors, color rendition, warranty, ease of installation and technical support, Lambert said. Vendors may provide a product selector to help security professionals determine the best product for the required distance and angle.
ALPR applications also require unique lighting. “An ALPR camera often has the shutter set to something like 1/1,000th of a second to prevent motion blur,” Lambert said. “This leads to around 20 times less light reaching the image sensor than traditional shutter speeds, such as 1/50.” ALPR cameras require additional lighting to optimize performance in both nighttime and overcast conditions.
A pulsed lighting system allows LEDs to deliver two to three times their normal brightness. Since the camera shutter opens, as opposed to staying on all the time, pulsing LEDs have prolonged operating life due to lower average temperatures, Lambert said.
Lighting technology has come a long way, and the increasing popularity of LEDs signifies a new era of cost-effectiveness and energy savings. Compared to alternatives, LEDs consume less energy and provide longer lifetimes and less heat emissions, Mellos said.
For surveillance, this translates to lower running costs, easier maintenance and a good conscience. A typical hospital project using 100 lights could save US$72,000 per year when factoring in running costs and replacement fees, Lambert said. “The long-life nature of LED technology allows the installation to last for more than 10 years, summing up the total cost saving to $0.7 million and carbon dioxide emissions reduction to 800,000 kilograms.” This is based upon 4,400 hours of usage per year at $0.16 per kilowatt per hour, with labor costs calculated at roughly $64 per bulb change.
However, lifetime cannot be determined simply by reading a specification sheet. Although LEDs are generally considered long-life devices, this is only valid if they are powered and controlled properly; the lifetime of an LED is directly related to its operating temperature. The length and scope of the warranty is also a sign of a manufacturer's confidence in its products.
With global warming becoming a growing concern, some municipalities mandate sites such as shopping centers or park lots to have their lights shut down after a certain time at night. “Surveillance systems are typically running 24/7, so using appropriate cameras for these sites is critical. If the cameras specified were designed to handle different lighting conditions, there would be problems,” Mellos said.
There is also the concern of light pollution. Excessive lighting can reduce quality of life or even cause health issues. Some municipalities have regulations in this regard, and it pays to understand local mandates to avoid unnecessary replacements and redesigns.
There are many types of IR illuminators to choose from, said John Huang, Deputy Manager of R&D at Camdeor Technology. “The intended application must be determined before comparing the specifications. For example, whether the whole scene or just a particular spot is to be lit directly affects how strong the intensity should be. While many people are firm believers of ‘the more the merrier,' more LEDs do not necessarily mean a longer range. There are illuminators that can project 80 to 100 meters with 25 LEDs, while others need 84 LEDs to project 30 meters.”
Furthermore, most security and surveillance cameras today use board mount or CS mount lenses, which could affect performance, Huang said. “CMOS sensors coupled with IR-cut filters and varifocal lenses are still for high-end, niche applications. As such, addressing color fidelity and reinforcing night vision are critical for day-and-night CMOS cameras. While these issues seem minor in indoor settings, outdoor applications place additional stress on cooling and color fidelity.”
When it comes to lighting design, there are dramatically different requirements depending on the application and the country, Lambert said. “Typically, because IR is only visible through a camera and performance is dependent on the quality of the camera, there are less guidelines covering IR.
However, recent British standards recommend that bullet cameras are not suitable for remotely monitored sites. Cameras with integrated LEDs around the lens can emit significant amounts of heat, attracting insects like spiders to nest nearby. This causes tedious maintenance problems as well as false alarms that waste law enforcement resources.
Stand-alone LED lighting generally contains a thermal management system and helps users comply with the standard, allowing them to qualify for faster police response. In addition, safety is a key concern in any security setting, and due diligence should be paid to avoid potential risks. Human eyes are very sensitive; intense beams of light can cause permanent damage. Although later revisions of the EN60825-1:2001 and IEC60825-1:2001 standards for laser safety have removed LEDs from their scope, some standards for LEDs are based on them.
According to the classifications within EN/IEC60825-1:2001, a Class-1 laser/LED device is safe to the naked eye under normal use. A Class-1M laser/LED device is safe for all conditions of use with the naked eye unless focusing or imaging optics are used to narrow the beam. The warning label notes: “Do not view directly with optical instruments.”