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Purchase surveillance cameras should be noted that the parameters
2011-08-10 09:03:52

 How to purchase surveillance cameras, surveillance cameras purchased to pay attention to what parameters? Here on this issue we talk about surveillance cameras to some of the key parameters
   
First, the sensor parameters

    
Currently, the mainstream surveillance camera image sensor with CCD element, in fact, photoelectric conversion element. And compared to the previous CMOS sensors, CCD sensitivity is CMOS 3 to 10 times, so the CCD chip can receive more light signals into electrical signals by the video processing circuit filtering, amplification, to form the video signal output . The received optical signal is stronger, the greater the amplitude of the video signal. Connect the video signal to a monitor or TV video input can see the video image. Improve the clarity of the image simply is to improve the camera's photographic capabilities.

Second, the lens parameters
    
Aperture: Aperture installed in the rear of the lens, the larger the aperture opening, the amount of light through the lens the greater the image resolution is higher; aperture as small, the amount of light through the lens smaller, more clarity of the image low. Usually F (flux) to represent. F = focal length (f) / aperture. In the camera's technical specifications, we can often see 6mm/F1.4 this parameter, which represents the lens focal length of 6mm, luminous flux of 1.4, then we can easily calculate the aperture of 4.29mm. In the case of the same focal length f, F value is smaller, the larger the aperture, the flux reaching the CCD chip, the larger the lens the better.

FOV parameters: in engineering practice, we used field of view to reflect the level of the screen shooting range. The greater the focal length f, the smaller field of view, the images formed on the sensor the smaller the range; the contrary, the smaller the focal length f, the larger field of view, the sensor range to form the larger picture.

Focal length (f) parameters: the focal length of the lens and the distance between the sensor, by changing the lens focal length, the lens can change the magnification, change the size of the image capture. When the distance between the object and the lens is very far, we can express the following formula: the lens focal length magnification ≈ / object distance. Increasing the lens focal length, magnification increases, vision can be closer to the screen of a small range, the vision to see more clearly the details; If you reduce the lens focal length magnification is reduced, to expand the scope of the screen, and can to see a bigger scene.


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