We often come across focal length in millimeters associated with CCTV Cameras . Most commonly used figure is 2.8mm. This value refers to the distance between the camera lens and the image sensor. Why is it important when selecting the right surveillance camera ? Focal length directly co-relates to the viewing angle of the camera. Here are the commonly used focal lengths and the associated viewing angles of IP Cameras 2.8mm = 90° viewing angle Most people assume that 90° angle is the best selection because it gives the highest angle of viewing . What is the catch ? Because wide angle lenses cover a large area they make the objects appear small. Therefor in areas where you need to identify small objects such as vehicle number plates In most indoor IP camera applications 2.8mm cameras can be used . However for outdoor applications , IP cameras with smaller viewing angles can be used . Each application is unique. Surveillance cameras with narrow viewing angles provides a smaller area of coverage. Which means you need to install more narrow angle IP cameras to get the same viewing area with IP cameras that have wide viewing angles.
4mm = 60° viewing angle
6mm = 45° viewing angle
12mm = 25° viewing angle
IP camera with 90° viewing angle may not be the best choice.