Lenses
Selection of the correct lens type is as important as the camera selection. A poor lens performance can significantly detract from the overall performance of the system.
Below are commonly used CCTV Lens terms.
Focal Length
The "focal length" of a lens is the distance between the optical centre of the lens and the imaging sensor.
Small focal lengths give a wide angle of view, and large focal lengths give a narrow angle of view.
Image Sensor
The image sensor is at the heart of any camera: captures view and converts to electronic signal. Sensor captures image and converts him into electronic signal. CCTV Cameras come in different chip sizes - 1", 2/3", 1/2", 1/3" and 1/4".
The Image Sensor size will affect the angle of view.
Angle of View
Angle of View is the area of a scene that a camera covers or sees. A large angle shows a lot of things very small, and a small angle shows fewer things, but bigger.
The angle of view can be calculated by the focal length of the lens and the size of the image sensor.
Quick reference table to find the appropriate lens for a given angle of view (horizontal)
Focal Length Image Sensor Size |
1.78mm |
2.1mm |
2.8mm |
3.7mm |
6mm |
8mm |
12mm |
16mm |
25mm |
1/4" | 91º | 81º | 65º | 52º | 33º | 25º | 17º | 13º | 8º |
1/3" | 107º | 98º | 81º | 66º | 44º | 33º | 23º | 17º | 11º |
1/2" | 122º | 113º | 98º | 82º | 56º | 44º | 30º | 23º | 15º |