What is the standard value of illuminance?

What is illuminance? What is the illuminance (LUX) value for low illumination? How many values ​​can be adapted to the surrounding environment in which the image is taken?

Illuminance is a unit that reflects the intensity of light. Its physical meaning is the luminous flux per unit area. The unit of illumination is the number of lumens per square meter (Lm), also known as Lux: 1 Lux = 1 Lm / square meter. Where Lm is the unit of luminous flux, which is defined as the amount of light radiated by the surface area of ​​1/60 square meters of pure platinum at a melting temperature (about 1770 ° C) within a solid angle of 1 steradian.

In order to have a perceptual understanding of the amount of contrast, the following calculation is performed. A 100W incandescent lamp emits a total luminous flux of about 1200 Lm. If the luminous flux is uniformly distributed on the half sphere, it is 1 m from the source. And the illuminance value at 5m can be obtained by the following steps: The radius 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 is the same, the radius is 5m The hemisphere area is: 2π × 52 = 157 square meters, the illuminance value at 5m from the light source: 1200Lm / 157 square meters = 7.64Lux

It can be seen that the illuminance emitted from the point source is obeying the inverse square law.

1LUX is approximately equal to the illumination of 1 candle at a distance of 1 meter. The minimum illumination (MINIMUM.ILLUMINATION) that we have in the camera specifications indicates that the camera can obtain a clear image only under the indicated LUX value. The smaller the value, the better, indicating that the sensitivity of the CCD is higher. Under the same conditions, the black-and-white camera requires much 10 times less illumination than a color camera that still has to handle color density.

General conditions: 100,000 LUX in summer sunshine; 10000 LUX in cloudy day; 100 LUX in indoor fluorescent lamp; 300 lux in 60 CM tabletop from 60W table lamp; 1000 LUX in TV station studio; 10 LUX in twilight room; 0.1 LUX in nighttime streetlight; 20CM far away) 10 ~ 15 LUX.

Illumination standard value classification

The illuminance standard values ​​are classified by 0.5, 1, 3, 5, 10, 15, 20, 30, 50, 75, 100, 150, 200, 300, 500, 750, 1000, 1500, 2000, 3000, 5000lx.

Lx (lux) is the unit of illumination.

The illuminance standard value is graded to visually perceive the minimum change in illuminance, and the illuminance difference is approximately 1.5 times. The grading is generally consistent with the CIE International Illumination Commission standard "Indoor Workplace Lighting" S008/E--2001.