A Guide to CCTV Lighting:
Part I: Essentials
The human eye and a CCTV imaging device have certain functionalities in common. Both are capable of receiving light reflected from an object, and both translate that light into a usable image. However, the scene illumination must be of sufficient intensity for that image to be intelligible.
We’ve all had the experience of looking at an object in dim light; the darker it gets, the more difficult it is to recognize the finer features of that object. The same is true of a CCTV camera.
But this is where the similarity ends. Unlike the human eye, CCTV cameras are available in a variety of configurations, each with a unique range of light sensitivities. This includes their response to different intensities and frequencies of light.
Camera response to different lighting frequencies
Different light sources elicit different responses from CCTV cameras. In the following table, we explore the advantages and disadvantages of various CCTV light sources.
| Light Source | Pluses | Minuses |
| Tungsten/halogen lamps (white light) | Accurate color response | Costly to operate |
| Metal halide & fluorescent (white light) | Accurate color response, more energy efficient | Relatively short operational life. |
| High-pressure sodium lamps (yellow light) | Performs well with black/white cameras | Poor performance with color cameras – inability to distinguish colors |
| Infrared illumination | Black/white cameras have good IR sensitivity, | Poor color rendition. May reverse light/dark in b/w cameras |
| LED lamps (white light) | Very low energy consumption. Long life. Excellent color rendition. Even illumination. | High cost per sq ft of illumination |
[1]
Light intensity
A typical camera specification states the minimum scene illumination required to produce a usable video image. Illuminations specification are measured in Lux.
If the Lux value of ambient lighting is insufficient to support the camera operation, supplemental lighting would be needed. Most environments, especially outdoor, are subject to extreme day/night and weather related changes, requiring some form of supplemental lighting.
Here are some typical Lux levels found indoor and outdoor environments:
- 50,000 Lux: Sunlight
- 10,000 Lux: Daylight
- 1,000 Lux: Overcast day
- 500 Lux: Indoor office
- 100 Lux: Dark day
- 1 Lux: Twilight
- 0.0001 Lux: Overcast night
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The calculation for the Lux output of supplemental lighting can be expressed by a simple formula:
Camera requirements in lux, minus available level of ambient lighting in Lux equals lux level of supplemental lighting required.
Here is a summary of the process to be followed when choosing luminaries to supplement camera operation.
Step 1 – Define each camera view.
Step 2 – Measure existing illumination levels at different times and locations within the scene using a light meter.
Step 3 – Choose luminaries required to increase ambient light from its current level to the level specified for each camera.
Step 4 – Adjust camera AGC (automatic gain control), BLC (backlight compensation), and iris control to regulate the amount of light reaching the camera image sensor to prevent underexposure, overexposure, flaring and other distortions.
Summary:
Neither all cameras nor all luminaires are created equal. Each exhibits unique operating characteristics. Designing an effective CCTV lighting system requires the correct matching of luminaires and camera imaging devices for a particular application.
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REFERENCES
[1] Simon Lambert BSc (Hons), R. (2018). CCTV Lighting Guide – IFSEC Global | Security and Fire News and Resources. [online] IFSEC Global | Security and Fire News and Resources. Available at: https://www.ifsecglobal.com/cctv-lighting-guide
[2] Networkwebcams.co.uk. (2018). Some Important Facts and Tips About Security Cameras and Minimum Illumination. [online] Available at: http://www.networkwebcams.co.uk/blog/2010/12/14/tips-facts-advice-security-cameras-minimum-illumination/