How to choose fixed focus and zoom lenses
At present, the focal length adjustment of the lens on the market is mainly divided into three types: one is fixed focus, the focal length is fixed, and the aperture is fixed; the other is manual zoom, which requires people to manually open the dome cover to adjust the zoom ring, usually the aperture is also fixed. The third is the electric zoom, which can control the zoom and focus of the camera on the video recorder or the matrix. The auto focus in all surveillance cameras is an automatic adjustment process after the lens changes the focal length. This process does not change based on whether there is any object movement in the monitoring range, but only changes the focal length of the camera itself. Some high-end cameras can automatically track moving objects within the monitoring range, and automatically change the focal length and focus during the automatic tracking process.
The selection of fixed focus and zoom lenses depends on the size of the monitoring range and the clarity of the monitoring scene. The relationship between the focal length of the lens and the angle of view of the lens is: the longer the focal length of the lens, the smaller the angle of view of the lens; the relationship between the lens specification and the angle of view of the lens is: the larger the size of the lens, the greater the angle of view of the lens. big. Therefore, under the condition of a certain object distance, as the focal length of the lens increases, the screen range of the monitored scene seen on the monitor at the end of the system is smaller, and the details of the screen are clearer; and as the lens specification increases , the screen range of the monitored scene seen on the monitor at the end of the system increases, and the details of the screen are blurred.