20 meters away with the number of mm monitor camera lens appropriate?
At the same time, the same focal length, length and width shooting range also with the camera CCD has a relationship. Charge - coupled Device, Charge - coupled Device. It is a semiconductor device that converts optical images into electrical signals. At present, most of the CCD chip used in the surveillance camera is 1/3 "and 1/4", that is, the target size is 1/3 inch and 1/4 inch. CCD target surface size, CCD and lens with the situation will directly affect the size of the field of view and image clarity.
According to the imaging principle, the smaller the focal length, the wider the field of view, but the distance is not clear. The larger the focal length, the narrower the field of view, but the longer the distance will be clearer.
1/4 "CCD lens in the line of sight with 1/3" CCD no difference, but the angle will be more narrow, while the shooting of the object will appear taller.
