System creation stages
• What light do you need – infrared or white?
• Have you made sure that illumination horizontal angle covers all field of view?
• What is the maximal range which needs to be illuminated? Determine the illuminator model on the assumption of required entrance angle and range.
• If white light is required be sure you use white light with appropriate spectral correction. Make sure that red, green and blue colors can be distinctly seen in the night time.
• If IR light is required than decide on the wavelength. Shorter wavelengths (such as 850 nm.) provide visibility of longer range while longer wavelengths (950 nm.) provide covert illumination but reachable range is shorter.
• Calculate maintenance and running costs of illumination system. Make sure you have chosen long-life illuminators with low power consumption.
• Consider the question of illumination placement. It should be installed thus none of the cameras would be directed on the source of light. The best solution is to install illumination at the same place where cameras are installed. You also need to pay attention if there any obstacles in the direction of surveillance and illumination. As for as light movement occurs in straight lines any obstacle (for example, spread tree) can create shadows.
• Pay attention to camera and lens characteristics. High-efficient camera and lens ensure high-quality image. To get the same result with a less efficient camera and lens one needs additional lighting.
• If illuminating equipment is used together with full-function dome camera then you need to choose between wide spanning angle illumination, limited area illumination or target region illumination. The best option here is to use wide spanning angle illumination because one can ensure 360 degree illumination for dome camera.
• Is light pollution an important factor? Excessive lighting is when light is used in excessive amount. If light pollution is not admissible at all then one needs to use IR illumination.

Camera sensitivity defines illumination minimal level required for sharp images. Despite the fact that manufactures often overstate the indicated rates, anyway these rates are the only available measurement methods. Sensitivity is usually measured in luxes. Black-and-white cameras are more sensitive than color ones. The higher is the resolution the lower is camera sensitivity. There exist no cameras with sensitivity zero exponent because any camera needs light to operate.

Lens diaphragm (aperture) defines the amount of light which transmit through it on the camera chip. Simply speaking the smaller is the aperture the more light transmits inside the lens. In the following table one can observe how the application of different apertures influences light transmission:

* = total lens diaphragm

IR-correction lens – such lens is projected in a way that there would be no problems of focal switch between day and night modes, it is made of special glass using coating technology which minimizes light diffusion. Defocusing is caused by different light wavelengths. Each separate wavelength is focused at different point after transmitting through the lens.

Color correction lens transmits only visible light and provides focusing of each separate color of visible light in the same point rendering thereby reference colors and sharp images. Color correction lenses are not for application with IR-illumination.

Illumination – as a rule the floodlight beam from the illuminator goes at a certain fixed angle. If requirements to illumination change or if camera coverage changes then illumination may become rejectable. It is quite often that the final decision on lens and surveillance area is taken straight at installment process. Changeable focal length lenses are used in many projects and illumination angle should also be changeable. The beam should be directed downwards in order to minimize its dispersion. To define the necessary illumination type one need to define the goal of all the system. White light provides possibility to illuminate the territory for pedestrians, staff and transport, it can be used as visible disincentive.

Illumination installment advices.

Illumination system running costs - 20% of all the expenditures in the world are connected with illumination. At that the bulk of them is spent on inefficient or unnecessary illumination. Illumination maintenance-and-running costs remain high. In the case of ordinary lamps’ application running costs are significantly higher than purchase and installation costs. As an example we may consider 500 Watts illumination from a lamp with an average life time of 3 months. Electricity costs are simply astronomical and at that every 3 months one needs to pay again for changing the lamps. LED technologies offer considerable economy of maintenance-and-running costs. LED electricity consumption level is 5-10 times lower. LED efficient life time is 30-40 times longer with considerably low costs on maintenance.

Required entrance angle determination: To obtain the best picture the angle at which the light hits the object should perfectly match the angle to which the camera and lenses are adjusted. Otherwise if the angle is too narrow the camera will see only a bright spot within its the field of view. Illumination at a very wide angle can lead to useless loss of energy and decrease of illumination range.

Required illumination range determination. Light follows the inverse square law: radiation intensity is inversely to square of range from light source. In practice it means that if an object moves away from a given point at a distance 2 times longer than the distance to the source of light, the object gets only the quarter of the light. So, an object located 10 meters away from the light source gets 100 luxes of light. If this object is 40 meters away, it gets only the 16th part of light, and as a result the object gets only 6,25 luxes.