What's the difference between a camera focal length of 2.8mm and 4mm?

Difference of focal length between 2.8mm and 4mm cameras;

1, the shorter the focal length, the larger the viewing angle. The wider you look. The longer the focal length, the lower the viewing angle. The smaller the range. The millimeter value of 2.88mm is small, and the millimeter value of 4mm is large. Comparatively speaking, the monitoring of 2.88mm is closer than that of 4mm, which is suitable for a small range. And 4mm monitoring is more suitable for a wide range of areas.

2. The greater the millimeter value of the lens of the surveillance camera, the farther you can see. However, the smaller the effective angle of the camera is, the thing with a small angle near the camera may not be in the effective range because it is outside its angle.

3. The smaller the millimeter value of the lens of the surveillance camera, the closer you look. However, the larger or wider the effective angle of the camera is, the things close to the camera with a large angle can be well blocked and seen clearly, otherwise it will be unclear if you look far away.

Camera or webcam is a kind of video input equipment, which belongs to a kind of closed-circuit television and is widely used in video conferencing, telemedicine, real-time monitoring and other fields. Cameras generally have the basic functions of video shooting, transmission and still image capture. After the image is captured by the lens, the image is processed by the photosensitive element circuit and control element in the camera and converted into a digital signal that can be recognized by the computer. Then it is input into the computer through the parallel port and USB connection, and then the image is restored by software, thus forming a picture. Cameras can be divided into digital cameras and analog cameras. Digital cameras can convert analog video signals generated by video acquisition equipment into digital signals, and then store them in computers. The video signal captured by analog camera must be converted into digital mode by special video acquisition card and compressed before it can be converted into computer. Digital camera can shoot images directly, and then transmit them to computer through serial port, parallel port or USB interface. The cameras in the computer market are mainly digital cameras, and digital cameras are mainly USB digital cameras with new data transmission interfaces, which are mostly visible in the market.