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Manual aperture and automatic aperture selection
- Apr 13, 2018 -

Lens aperture is divided into manual and automatic two. In the past, due to the use of cameras in the outdoors or other special occasions, auto iris lenses were more often used. In the current monitoring project, due to the extensive use of CCTV systems in smart buildings, indoor surveillance sites account for a high proportion. Many engineering companies also like to use automatic iris lenses when making engineering equipment quotation. Although the auto iris lens is more adaptable to light changes at the monitoring point, its price is also significantly higher than that of a manually fixed focus lens with the same focal length. Most cameras now have electronic shutters, and the indoor light source is relatively stable. Therefore, it is not necessary to use a large number of auto iris lenses in smart building projects; on the other hand, the automatic iris lenses used in the market are now divided into two. Major categories: a. Power-driven auto iris lens; b. Video-driven auto iris lens.

The power-driven automatic iris lens controls the lens through four wires, two of which are DC12V or DC24V power to drive the motor in the lens, and the other two control wires control the iris by sensing the illumination of the external light source through the light sensing point in the lens. Size; video drive auto iris lens is controlled by three lines to the lens, one for the video trigger signal to start the aperture, and control the aperture size, and the other two for the DC12V or DC24V power line drive motor motor. Although most black-and-white or color cameras on the market today have automatic iris lens interfaces, most cameras are not compatible except for a few lenses that are compatible with two lenses. They can only use power-driven auto iris lenses or video-driven auto iris lenses. If some cameras are damaged during use, the newly purchased camera will have problems with the original auto iris lens. However, when the monitoring point in the project is outdoors, it is necessary to use a lens with an automatic aperture, because the dynamic range of the outdoor light changes greatly, the ambient illuminance in the summer sun reaches 50,000Lx-100000Lx, and only 10Lx in the nighttime streetlight. The magnitude of change is considerable. In this case, whether or not the camera has the auto-adjustment sensitivity function, that is, through the electronic shutter of the camera itself, it is impossible to adapt to such a wide illumination range, and it is impossible to achieve the effect of controlling the image effect.

 

How to correctly select the camera lens according to the monitored environment in the TV monitoring system is very important, because it directly affects whether the effect of the monitored surface painting seen by the system on the end monitor of the system can meet the requirements of the system. Design requirements (in terms of screen area or image details), so the correct choice of camera lens can make the system optimal design and get a good monitoring effect.