Lighting Design Guide White PaperSource: Axis Communications
When selecting a network camera for day or night surveillance, there are several elements impacting image quality that are important to understand. This guide is intended to give a basic overview of those elements, to give an understanding of how lighting affects the image, and of the factors that need to be taken into consideration for creating favorable lighting in dark environments.
Light is fundamental to network video. It is light reflected from the scene being viewed that allows images to be visible both to the human eye and to the camera. So the performance of any network video system depends not only on the camera and lens, but also on the quantity, quality, and distribution of available light.
Light is energy in the form of electromagnetic radiation. The light's wavelength (or frequency) determines the color and type of light. Only a very narrow range of wavelengths is visible to the human eye, i.e. from approximately 400nm (violet) to 700nm (red). However, network video cameras can detect light outside the range of the human eye, allowing them to be used not only with white light, but also with Near Infrared light (715-950nm) for night surveillance.
The behaviour of light varies according to the material or surface it strikes, where it is either reflected, diffused, absorbed or (more commonly) subjected to a mixture of these effects. Most surfaces reflect some element of light. Generally, the paler the surface, the more light it reflects. Black surfaces absorb visible light, while white surfaces reflect almost all visible light. Infrared is not always reflected in the same way as visible light.