What is the minimum illumination of the camera? Seek an answer

Q: What is the minimum illumination? What is sensitivity? What does 0.000 1Lux stand for? A: Minimum illumination is a way to measure camera sensitivity. In other words, the camera can see available images in dark conditions. However, because there is no international standard for management, every large CCD manufacturer has its own method to measure CCD sensitivity. But a camera marked with (1Lux, F 10) can be exactly the same as a camera marked with (0.0 1Lux, F 10)! ! ! Is that weird? Why? In addition, the most commonly used method to measure the minimum illumination is called the target illumination method, and the target illumination indicates how strong the light reaches the position where the CCD surface is placed. Although the clear definition is different, there are three main parameters that determine the result. That is: F stop (lens used to test the aperture of a camera) color temperature (color temperature of light source, that is, spectral content) IRE (IRE level of video amplitude) reflectivity (reflectivity and background of the target) F stop is a method to measure the focusing ability of a lens. A good lens can collect more light and concentrate it on the CCD sensor. The lens of F 1.4 can collect twice as much light as the lens of F2.0 In other words, the lens of F 1.0 can collect 100 times more light than the lens of F 10, so it is very important to mark F stop in the measurement, otherwise the result is meaningless. Color temperature Color temperature is a method to express the wavelength content of light in a light source. Most of the wavelengths of 3200k light source are between 600 nm and 900 nm, while most of the wavelengths of 9300k light source are between 300 nm and 500 nm, so different color temperatures will completely change the test results. On a typical CCD sensor, a light source with a wavelength of 600 nm generates more electrons 10 times than a light source with a wavelength of 900 nm. This is why the results are marked with color temperature. The maximum video output amplitude of IRE CCD camera is generally set to 100 IRE or 700 mV. The video with 65,438+000 ire can completely drive a monitor to display high-quality images with the best brightness and contrast. A video with 50IRE only represents half the contrast, while a video with 30IRE or 265,438+00 mv only represents 30% of the original amplitude. Generally, 30IRE is the lowest value representing available images. When the automatic gain of a standard camera is increased to the maximum gain, the noise level should be 10IRE, so it can provide an acceptable image with a signal-to-noise ratio of 3: 1 or 10dB. A result measured at 10IRE can be 10 times higher than that measured at 100IRE, so the result without marking the IRE grade is actually meaningless. The reflectivity and background of the target can completely change the measurement results. A target plane with a reflectivity of 100% generates 100 times more light than a target with a reflectivity of only 1%. How to set the parameters: Generally, reputable companies will measure the sensitivity under the following standards. F stop F 1.2 color temperature 5600K video level 30 IRE reflectivity is 80%, so sincere camera manufacturers will mark the minimum illumination 3 lux (F 1.4 5600K 30 IRE 80%) as follows. If any parameter is omitted, the result may be different by a factor of 10 to 1000. For example, the same camera can mark completely different1lux (f1.45600k30IRE 80%) 0.001lux (f0.755600k10IRE1%). Some irresponsible manufacturers will label the ultra-high sensitivity camera1lux (f1.4 5600k30ire 80%) as follows, but it is labeled as 0.000 1 lux. Now you should know why! ! ! Because they are marked under the following conditions (F0.755600k10IRO.1%), do you want to know what this (F0.755600k10IRO.1%) means? F 0.75 is a kind of lens that will cost you $30,000 or more, and is generally not used in the closed-circuit monitoring industry. 10 IRE video is below the noise level, so nothing can be seen. The reflectivity of 0. 1% can only be obtained by placing a thin white line in a completely dark background.