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Four factors that determine the advantages and disadvantages of low-light cameras
With the progress of the monitoring of low-light technology, the application and manufacturing of low-light cameras have also become more mature. Most camera manufacturers have developed the lower illumination conditions of the image machines, roughly from 1.0 lux to now 0.001 lux, etc. So, these cameras really have such a low low-light sensitivity? Or bragging mostly? In order to distinguish the advantages and disadvantages of low-light cameras, we teach you to distinguish between the following four factors to do good and bad.
The first is the lens used
As an important part of the low-light camera, the lens function is to focus the camera's Sensor on the desired light of the subject, so that the image is normal. The amount of light that the lens can capture directly determines the sharpness of the CCD or CMOS sensor image. Therefore, the condition of how much light is taken on the lens is measured, and we call it the amount of incoming light F. The amount of light entering the lens is expressed by the application of the F value (aperture). F value = f (focal distance) / D (effective aperture of the lens), which is inversely proportional to the aperture, and is proportional to the distance from the focal point. With the same focal length, the larger the lens diameter, the smaller the F value and the greater the amount of light entering the lens. The F value of common lenses is mostly 1.2, 1.4, of course, there are currently shots up to F1.0, but after all, it is a minority. Therefore, in order to make the low-light camera get excellent low-light effect, with the appropriate F-value lens has become the key factor.
Secondly, CCD/CMOS Sensor photosensitive assembly
At present, there are several suppliers of CCD/CMOS commonly used in low-light cameras: SONY, SHARP, Aptina, Omnovision, LG, etc. Among these CCD/CMOS suppliers, SONY's CCD has relatively good brightness, which is commonly used. The SONYCCD low illuminance technology is Super HAD CCD; Later, there is an ultra-luminosity Exview CCD, and the CCD has an sensitization sensitivity of 5 times that of the Super HAD CCD. CMOS has increased in the number of pixels and light into the way to improve, SONY and APTINA and OMNIVISION have a large size and high sensitivity 1000mV Sensor introduced to meet the needs of low-light IP cameras.
In addition, the size of the CCDC/MOS components also has a great influence on the brightness, and the larger the size, the better the brightness. In order to make low-light cameras have lower illumination requirements, manufacturers usually use 1/1.8, 1/2-inch CCD/CMOS sensors. There is also data in the component manufacturer's specification table showing that the 1/3-inch CCD's incoming light sensitivity is only about 56% of that of the 1/2-inch CCD, while the 1/4-inch CCD has only 1/3 inch more. 44% of CCD. This can confirm that the size of the photosensitive component is also one of the key factors that affect the low illumination of the snake machine.
Image DSP processor components
Low-illuminance camera technology has been developed not only in lens hardware technology and photosensitive components research and development improvements, some DSP image processor in the camera also have some technology is related to the low-light camera image performance, these image processing technology is comparable DSS low-speed electronic shutter, ie, frame accumulation technology, also has a color-to-black-and-white signal portion, but usually the camera manufacturers in this part focus on the application of low-speed electronic shutter image processing technology. This is a low-light-reducing camera. Another tiny key factor in the effect.
The last factor is the color to black and white technology
In general, the sensitivity of a pure black-and-white camera will be much higher than the sensitivity of a color camera. Because the DSP image processing in a black-and-white camera requires only black-and-white and color processing, camera manufacturers are now manufacturing most of the low-light cameras. Most of them have a color to black and white function, that is, a color image during the day, and the image is converted to a black and white image by a DSP image processor at night to obtain a lower night vision illumination. The general color to black and white conversion process is to control the degree of image switching by converting the charge (current) after the CCD/CMOS collection light to the current level. When the current reaches a certain critical value, it will automatically switch to a black and white image. Do not allow the camera to repeatedly switch the camera color from the edge of the current threshold. Usually, a time delay processing circuit is used to control the color and black and white switches of the camera.
Through the above explanation, I believe that each user has learned how to determine the merits of the low-light camera based on four factors, rather than the minimum illumination number that the manufacturer believes on the specification sheet, and in addition to the four low According to camera selection factors, the application environment, users need to seek, monitor the target content of these conditions is also an important condition to choose low-light camera can not be ignored.