Light
The human eye and the camera lens operate on completely different lines.
Although the human eye adjusts automatically to various light conditions,
the camera is inherently less flexible.
In a CCTV system,lighting has to be ‘designed in’ from the beginning if the best
results are to be obtained.The type of lighting used, and the correct positioning,are
vital to maximum security.
Everyday ‘white light’ is actually a mixture of colours of different frequencies.
CCTV is more receptive to certain colour combinations than others.The best results
are usually obtained by matching the spectral response of the camera to the light
illuminating the scene.
The amount of light reflected from an object determines how ‘bright’ it appears.
Here are some typical reflective figures:
These figures relate to the minimum level of lighting required for security purposes
to everyday light.It can easily be seen that today’s CCTV technology will give good
results under very low light levels.Sony ‘Exwave’ cameras can operate in colour as
low as 0.8Lux (F1.2) without switching to monochrome or reducing frame rate.
8The Sony Guide to CCTV .Issue 3
Asphalt 5%
Foliage 10-20%
Concrete 25-30%
Red Brick 35%
Snow 95%