Explanation of terms in closed circuit monitoring (1)

1) What is the meaning of CCTV?

Answer: CCTV is the abbreviation of Closed Circuit Television in English, which means closed-circuit television monitoring system
2) What is the focal length of the lens?

Answer: From the optical principle, the focal length is the distance from the focal point to the center of the lens. That is the focal length. For example, "f = 8-24mm," means the focal length of the lens is 8-24mm

3) What is the relationship between focal length and imaging size?

Answer: The focal length is proportional to the imaging size. The longer the focal length, the larger the imaging, and the shorter the focal length, the smaller the imaging. The focal length of the lens is inversely proportional to the viewing angle. The longer the focal length, the smaller the viewing angle, and the shorter the focal length, the larger the viewing angle.

4) What is the relationship between focal length and depth of field perspective?

Answer: The focal length is inversely proportional to the depth of field. The longer the focal length, the smaller the depth of field, and the shorter the focal length, the greater the depth of field. The focal length is inversely proportional to the strength of perspective. The longer the focal length, the weaker the perspective, and the shorter the focal length, the stronger the perspective
5) What is the camera's back focus adjustment?

Answer: When a standard lens is installed, if the image of the subject is exactly on the target surface of the CCD image sensor, a fixed lens can be used, and the method of adjusting the position of the ccd is called this method.
6) What is the lens F value?

Answer: F value refers to the brightness of the lens. The <1.2> of the <maximum aperture ratio 1: 1.2> shown in the lens specifications is the F value. The smaller the F value, the higher the brightness of the lens. Each time the F value is reduced by one step, the brightness increases twice. The amount of light incident on the lens is proportional to the cross-sectional area of ​​the light beam [the effective aperture of the lens [D] squared], so the image brightness is inversely proportional to the square of the F value. It is estimated from this that each time the F value is reduced by one step, the brightness increases twice.

7) What is the aperture of the lens?

Answer: The function of the aperture is just like the rainbow frog in our human eyes. It is mainly used to adjust the light input of the camera. F represents the aperture of the lens, and a smaller F value represents a larger aperture.
8) What is the depth of field?

Answer: When an object is in focus, all scenes from a certain distance in front of the object to a certain distance behind it should also be clear. The distance from front to back where the focus is quite clear is called the depth of field
9) What is a wide-angle lens? (Wide Angle)

Answer: The wide-angle lens has a very short focal length, so the scene projected on the film becomes smaller. The wide-angle lens shooting angle, in addition to shooting more scenes, can also shoot wide-angle images in a narrow environment. The viewing angle is more than 90 degrees, the observation range is large, and the image is deformed in the vicinity.

10) What is a telephoto lens?

Answer: The angle of view is within 20 degrees, the focal length can reach tens of millimeters or hundreds of millimeters