What is illuminance?

What is illuminance?

What is illuminance? What is the illuminance (LUX) value for low illuminance? How many values ​​can adapt to the surrounding environment of the captured image?

Illuminance is a unit that reflects the intensity of light, and its physical meaning is the luminous flux irradiated on a unit area. The unit of illuminance is the number of lumens (Lm) per square meter, also called Lux: 1Lux = 1Lm / square meter In the formula, Lm is the unit of luminous flux, which is defined as the amount of light radiated by pure platinum at a melting temperature (about 1770 ° C) with a surface area of ​​1/60 square meters within a solid angle of 1 sphere.

In order to have a perceptual understanding of the amount of contrast, the following is an example for calculation. The total luminous flux of a 100W incandescent lamp is about 1200Lm. If it is assumed that the luminous flux is evenly distributed on half of the sphere, it is 1m away from the light source. The illuminance values ​​at 5m and 5m can be obtained by the following steps: The area of ​​the hemisphere with a radius of 1m is 2π × 12 = 6.28 square meters. The illuminance value at 1m from the light source is: 1200Lm / 6.28 square meters = 191Lux, the radius is 5m The area of ​​the hemisphere is: 2π × 52 = 157 square meters. The illuminance value at a distance of 5m from the light source is: 1200Lm / 157 square meters = 7.64Lux

It can be seen that the illuminance emitted from the point light source follows the inverse square law.

1LUX is approximately equal to the illuminance of 1 candle at a distance of 1 meter. The minimum illuminance (MINIMUM.ILLUMINATION) that we commonly see in the camera parameter specifications means that the camera can obtain a clear image screen only under the LUX value marked. The smaller the value, the better, indicating that the sensitivity of the CCD is higher. Under the same conditions, the brightness required by a black and white camera is much lower than that of a color camera that still has to deal with color density.

General situation: 100,000 LUX in summer sunshine; 10000 LUX in outdoor outdoors; 100 LUX in indoor fluorescent lamp; 300 LUX from 60W desk lamp 60CM desktop; 1000 LUX in TV station studio; 10 LUX in dusk indoor; 0.1 LUX in night street lamp; candlelight ( 20CM away) 10 ～ 15LUX.