Apart from providing rich source of information within our website, we have also provided external links below to some of the most interesting CCTV design resources:
There is a document called “CCTV Operational Requirements Manual” from UK Home Office Scientific Development Branch. This manual helps to understand the concept of recognition, detection and identification used in IP Video System Design Tool.
There is a very interesting and useful video from FBI. This video explains how to avoid common CCTV design problems such as using wrong camera lenses, installing cameras in the wrong locations, using low FPS and wrong compression and much more.
Wide angle lenses have many advantages for CCTV and IP video surveillance. The first advantage is wide field of view (See images bellow). The second advantage is good low-light performance. And last but not least, wide angle lenses provide good depth of field as compared to telephoto lenses. However these advantages do come with a few drawbacks as well such as the possible geometrical distortion which appears as visible curvatures at the edges of a camera image and higher requirements for the camera resolution.
Hence it is important to maintain a proper balance between the wide field of view and possible drawbacks of wide angle lenses.
To find a proper focal length for wide angle lens, the CCTV designer needs to perform many calculations. To ease the lens selection the designer can use special 3D CCTV design software where you can clearly see all 3 parameters: actual field of view, lens distortions and camera resolution.
When rays of light pass through a convex lens (the shape of lens shown in figure above) they tend to converge at a single point at some distance ahead of the lens. This distance between the lens and the point where they focus is known as the focal length as specified by the symbol f in the figure. In case of a CCTV camera, the lens focuses the rays at a point where the sensor is placed.
The combination of the focal length of the lens and the size of the sensor determine the field of view of the CCTV camera. The shorter the focal length, the wider the field of view, and vice versa.