Basic knowledge about camera FOV
As the golden eye of the whole monitoring system, the camera is responsible for keeping an eye on all the details of the monitoring occasions. Its “vision” is very important. Now, Xiaojin will briefly introduce some tips about the camera’s field of view angle:
Field of view (FOV for short) refers to the range that can be covered by the lens (objects beyond this angle will not be collected in the lens). The range that a camera lens can cover is usually expressed in terms of angle, which is called the FOV of the lens. Generally speaking, the angle formed by the limit of the range you can see by rotating your eyes while keeping your head still in front of the screen is called the field angle.
The area covered by the visible image formed by the subject through the lens on the focal plane is the field of view of the lens, which is represented by the angle between the two sides of the display and the eye line.
The larger the field angle is, the larger the field of view is, and the smaller the optical magnification is. Generally speaking, if the target object exceeds this angle, it will not be collected in the lens. The field angle is divided into horizontal field angle, vertical field angle and diagonal field angle.
Calculation method of field angle
In the actual test, the field angle can be calculated according to the following formula:
The half field width and object distance need to be measured.
Assuming that the whole lens system is regarded as an ideal lens, the field angle can also be calculated as follows:
Through the definition of field angle, we can draw the following conclusions:
- The field angle is inversely proportional to the lens focal length. Generally, the larger the lens focal length is, the smaller the field angle is.
- The field angle is proportional to the effective imaging size of the sensor. The higher the effective imaging height of the sensor, the larger the vertical field angle, the wider the effective imaging width of the sensor, and the larger the horizontal field angle.
Classify lenses by field angle
● Standard lens: the viewing angle is about 30 degrees, and the use range is wide.
● Tele lens: the angle of view is within 20 degrees, which can be shot from a long distance.
● Wide angle lens: the viewing angle is more than 90 degrees, the observation range is large, and the near image is deformed.
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