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POWER TO THE PEOPLE Achieving good lighting performance and accurately specifying and comparing illuminators has long been a challenge for installers and security buyers. Here Tony Whiting, joint MD at Raytec, reveals exclusively to SME, how Raytec has tackled this problem by publishing the industry’s first lighting standard for surveillance In conjunction with your choice of camera and lens, the right lighting is the most powerful tool in helping you to achieve outstanding night-time performance from any professional video surveillance system. But with many different lighting products available in the market today, it can be difficult to accurately compare the performance of different illuminators. At one level, this may seem fairly straightforward – just look at the claimed distance performance from the manufacturer. However until now, there has been no standard way to evaluate different illuminators and their performance claims – particularly InfraRed lighting. And crucially, there have been no standardised testing methods for manufacturers to adhere to. Traditional lighting industries ie street/urban/commercial lighting et. have long established and standard testing methods allowing all illuminators to be accurately compared. Sadly, this is simply not the case for lighting for surveillance and security. Without standards – distance and image quality interpretation varies greatly. Consider the two Infra-Red images on the right (Figure 1 and 2) from different manufacturers (subject at 70m). Each manufacturer may try and argue that their illuminator delivers a distance of 70m+, but clearly one product significantly outperforms the other. As we can see the image on the bottom is far superior, delivering more clarity and detail, and less noise – ultimately helping the user to achieve far better analysis and identification.
Figure 1
Open to interpretation Surveillance lighting manufacturers currently publish very limited information – mostly quoting a maximum lighting performance distance. But with the absence of standardisation, methods for calculating performance, especially distance, have always been left open to interpretation - leading to varying claims. Consider two products from different manufacturers with exactly the same light output. One manufacturer may take a realistic view and quote a distance of 150 metres (~492 feet) but the other may take an overly optimistic view and rate this same product for 250 metres (~820 feet). Who is right? Since both products actually deliver exactly the same light output, it is obvious that the illuminator from the realistic manufacturer is going to provide a much better picture at its quoted distance than the other illuminator at its quoted (overly-optimistic) distance. The manufacturer with the better claimed distance may have: n n
used a much more sensitive camera used a much more expensive and higher performing lens
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Figure 2
n n
tested against a highly reflective surface accepted a much noisier picture to quantify the published distance
Distance is only one area of lighting performance to consider. Other criteria to consider include: angle, flexibility and adaptability, integration capability, consumption, environmental impact, reliability, lifetime, warranty, customer support and lighting partner credentials. With no agreed performance measurements and standards, security professionals have therefore been unable to safely rely on some lighting manufacturers’ performance claims and are unable to easily 8 compare different products.
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Figure 3
8Towards standardisation
As the leader in LED surveillance lighting systems, and after facing this challenge for the last 25 years, Raytec has taken the lead in coordinating the publication of the first ever Lighting Standard for Video Surveillance Applications – ‘POWERS’ which addresses all of the above issues and more. Based on decades of the hands-on and practical industry experience of the authors, the new standard sets a lighting performance benchmark backed up by consistent scientific testing methods. It highlights the relevant criteria to consider, enabling security professionals to more easily specify and reliably compare the performance of different illuminators. It also helps them gain an understanding as to how their chosen lighting product will perform. When looking at a product, customers ultimately want to know: How far does my light shine? How wide does it shine? Is it efficient and reliable? What features does it have? Will the manufacturer support me with warranty/certification/tech support? To answer these questions, the “POWERS” standard looks at the following areas: P O W E R S
Pp Peak Power Op Overall Power Width/Angle Environmental Reliability Specification/Features
The ‘POWERS’ lighting standard explored Firstly, calculating accurate lighting distances should be based around achieving a standardised level of lighting power on scene at your required distance to ensure a standardised quality of image every time. But what is classed as acceptable light power on scene and what method has been used to calculate this? Peak Power should be the measurement used by all manufacturers to properly calculate their quoted performance distances. The Peak Power of an illuminator is measured at the centre point of the beam using an appropriate light or power meter. At Raytec, we measure all our units at three metres from the light source. The inverse square law is then applied to calculate the amount of lighting power on scene at the quoted distance. To achieve what we at Raytec would consider to be high quality images and to comply with this new standard, we recommend that the power on scene should be a minimum of 0.35uW/cm2 for IR and 3 lux for WL – and we guarantee this for all Raytec products. The Overall Power output (Total Flux) is also an important measurement for calculating the overall efficiency, when Total Power Consumption is compared to Overall Power Output. It is typically
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Figure 4
measured in an integrating sphere by an independent testing house or can be calculated from first principles, and it is measured in Watts (IR) or Lumens (WL). Determining Width/Angle is another important area which is currently left open to the interpretation of the manufacturer. In the two images above (Figure 3 and 4), both manufacturers could claim a 60 degree beam angle. Whilst the manufacturer on the left could technically claim that their illuminator does actually provide light throughout the full scene, we can clearly see that the image on the right is far superior, evenly covering the full width and depth of the scene with no dark or bright areas. But how should manufacturers decide the illumination angle of their product? A standard measurement to determine width/angle is the ‘Full Width, Half Maximum’ (FWHM) approach. It is well-known in many traditional lighting industries and this is the approach adopted in the ‘POWERS’ standard. It takes the peak power reading in the centre point of the beam and then records the angle at either side of centre at which lighting power has dropped to 50%. This measurement helps to provide an understanding of the beam angle provided by illuminator. Lighting manufacturers should be able to provide a plot of their products’ power output against the angle output – this can be simply recorded in a darkroom environment using a light/power meter. Raytec recommend that a cut-off point of between 30-50% of peak power is generally acceptable. The ‘POWERS’ standard quotes the angle achieved at both the 50% and 25% points versus peak power. With this data, customers will be able to accurately evaluate the quality of the beam spread and it will help them understand how to reliably compare the angle output of different lighting products. Other criteria to consider include: n
n
Environmental – including the efficiency of the unit, whether the unit meets RoHS, REACH, WEEE requirements and whether the manufacturer has ISO14001 accreditation. Reliability – including the duration, terms and any exclusions within the product warranty, confirmation of certification including CE, EMC, UL, CSA, eye safety etc. and whether the manufacturer has ISO9001 accreditation.
A vitally important part of the reliability factor to consider is how the manufacturer has calculated their products’ quoted lifetime. Historically this has also been very subjective. A standard calculation to determine end of life, followed by ‘POWERS’ (and well-known in traditional lighting industries), is the L70/B50 approach. It determines the end of an illuminator’s life to be when a batch of 50% of the LEDs 8 (in a single illuminator) has dropped to below 70% of their original
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Figure 5
8power. There are many factors affecting an illuminator’s lifetime, but
most reputable lighting manufacturers should be able to provide their products’ lifetime curve (power against time) – or how else did they calculate their lifetime claim?
Specification/features It is also important that your chosen illuminator can provide the level of functionality needed to meet your installation requirements. As an absolute minimum, your illuminator should provide: Photocell, Photocell Adjust, Power Adjust and Telemetry Control. Desired features could include: adjustable angles, photocell following output, hot-spot reduction technology. Advanced features could include: remote controller, timer function, IP addressable.
The future of surveillance lighting standardisation Raytec has invited all major lighting manufacturers to play an active role in helping to formulate this new standard and are delighted to advise that they have generally agreed with the theory behind ‘POWERS’. Hopefully in time, all reputable manufacturers will commit to measuring their lighting performance in accordance with the standard and publish the proposed information so that customers can have consistent and reliable information on which to base their choices. In addition, Raytec will offer testing of third party products in accordance with the standard, so where there is no published information available, Raytec will measure the product and provide the relevant information. Going forward, we will be publishing ‘POWERS’ information for all our new and A-line products and will continue to work closely with
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Figure 6: Example of “POWERS” data for Raytec VARIO2 model (product launching Jan ‘16)
other manufacturers and customers to evolve the standard over time in accordance with technology advances. We guarantee that at Raytec we are working hard to ensure that the standard becomes widely adopted and used for the benefit of everyone across the industry. n
To learn more on the ‘POWERS’ standard visit www.rayteccctv.com to
listen to the first webinar on the new standard – or alternatively email sales@rayteccctv.com or call: +44 (0) 1670 520055