The focal length is the distance from the center point of the lens to the clear image formed on the glue plane. The size of the focal length determines the size of the viewing angle. A small focal length value means a large viewing angle and a large observation range; a large focal length value means a small viewing angle and a small observation range. According to whether the focal length can be adjusted, it can be divided into two categories: fixed focus lens and zoom lens.
Expressed by F, measured by the ratio of the focal length of the lens f to the clear aperture D. Each lens is marked with a maximum F value, for example, 8 mm/F 1.4 means that the maximum aperture is 5.7 mm. The smaller the F value, the larger the aperture, and the larger the F value, the smaller the aperture.
Corresponding to the largest sensor size:
The maximum sensor chip size that the lens imaging diameter can cover. There are mainly 1/2"", 2/3"", 1"", 4/3"".
How the lens and camera are connected. Commonly used include C, CS, F, V, M42, M75, etc.