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Minimum illumination
- Apr 13, 2018 -

The minimum illuminance is the illuminance of the scene when the illuminance of the photographed object is low to a certain degree and the video signal output from the camera is lowered to a predetermined value. The minimum illuminance of a general color camera is 2 to 3 LUX. The illuminance is determined on the basis of a certain lens aperture factor. Therefore, it is not possible to look at the minimum illuminance indicated in the camera specification, and the illuminance value of the camera should be the same under the same aperture factor. size. The lower the minimum illumination, the higher the camera grade. Compared to color cameras, black and white cameras are only sensitive to light intensity (brightness) signals due to lack of color processing, so the illumination of black and white cameras is lower than that of color cameras. Generally, 0.1LUX can be achieved at F1.4. As for the low light camera, it is even lower. See the lens section for information on the aperture coefficient.

The nominal value of the video signal is 1Vp-p, the standard value is 0.7Vp-p, and the video signal value at the lowest illumination is 1/3 to 1/2. Therefore, the image of the camera at the lowest illumination level will never be "like white." In addition, the sharpness of the image produced by the camera at the lowest illumination is measured by a TV signal test card. The black and white stripes require a black reflectance of approximately 0% and a white reflectance of greater than 89.9%. However, we sometimes do not have such conditions when we observe the scene. For example, the reflectivity of leaves and grass is very low, and the contrast is very small, so it is not easy to obtain clear images. Therefore, in practice, the nominal minimum illumination of a camera cannot be used as a measure of the ambient illumination.