The Relationship Between Camera Lens Focal Length and Angle

The relationship between camera module focal length and angle:

Focal length: The distance from the center of the lens to the image plane (usually the sensor or film).

Field of view ( FOV) angle: The angle of the spatial range that the lens can capture.

The shorter the focal length, the larger the FOV angle, and the wider the scene range that can be captured.

The longer the focal length, the smaller the FOV angle, and the narrower the scene range that can be captured.

Application scenarios for wide-angle lenses.

Focal length range: Typically between 2.8mm and 16mm.

Surveillance angle: For example, a 2.8mm lens can provide an FOV angle of approximately 120 degrees, suitable for scenes requiring wide coverage, such as corridors or halls.

Recommended distance: Lenses with shorter focal lengths can provide clear images at closer distances, but may not cover longer distances.

Application scenarios for telephoto lenses.

Focal length range: Typically over 16mm.

Surveillance angle: For example, a 16mm lens can provide an FOV angle of approximately 19.8 degrees, suitable for scenes requiring long-distance monitoring, such as watching activities far away.

Recommended distance: Lenses with longer focal lengths can provide clear images at longer distances, but may not cover closer distances.

Focal length not only affects the FOV angle but also directly influences the DOF. DOF refers to the range from the foreground to the background that is in clear focus. The shorter the focal length, the larger the DOF, with a noticeable background blur effect, suitable for highlighting the subject. The longer the focal length, the smaller the DOF, with a clearer background, suitable for scenes requiring precise focusing.

The size of the aperture also affects the DOF. A larger aperture (lower F number) increases the DOF, making both the foreground and background clearer. A smaller aperture (higher F number) decreases the DOF, blurring the background and highlighting the subject.

In summary, there is a close relationship between the focal length and angle of camera modules. Choosing the right focal length and aperture is crucial for achieving the best surveillance effect.