What is Lumen?

Lumens, a unit of luminous flux. The luminous flux of a point light source with luminous intensity of 1 Candeira (cd) in unit solid angle (1 sphericity) is ldquo 1 lumen rdquo, abbreviated as (lm). The definition of lumen is lumen, which simply refers to the brightness of a candle at a distance of one meter (1 m = 1 m). The luminous efficiency of an ordinary 40-watt incandescent bulb is about 0/0 lumen per watt/kloc, so it can emit 400 lumens of light. A 40-watt incandescent lamp has a luminous flux of 340 lumens at 220 volts. Luminous flux is the ability to describe the intensity of visual response produced by light source radiation in unit time, and the unit is lumen, also called brightness. The unit of projector luminous flux is ANSI lumens, which is the standard for measuring projector luminous flux formulated by the American National Standardization Association. It measures the ANSI lumens of the projector on the screen by multiplying the illuminance of each point of the nine intersections of the glyph by the area, and then finding the average of the nine points. The higher the lumen value, the brighter it is. The higher the brightness, the less need to turn off the lights when projecting. ANSI stands for American National Standards Institute. General luminous efficiency (lumen/watt) incandescent lamp, 15 white LED, 80-200 fluorescent lamp, 50 solar lamp, 94 sodium lamp, 120 energy-saving lamp, 60-80 LED, 80- 130 Definition: 1967 France. Candlelight, international candlelight, Candeira (candela), under the standard atmospheric pressure of per square meter 1 0/325 Newton, an absolute ldquo bold rdquo with an area equal to 1/60 square centimeters (that is, an ideal object that can absorb all external light without reflecting), at the solidification temperature of pure platinum (Pt) Moreover, the three concepts of candlelight, international candlelight and Candeira are different and should not be equated. In terms of quantity, 60 Candeira is equal to 58.8 international candle, and the 1 candle of Hefner lamp is equal to 0.885 international candle or 0.9 19 Candeira. 2. Luminous intensity and brightness Luminous intensity is short for light intensity, and the international unit is Candeira (short for cd). Lcd refers to the luminous flux emitted by a light source in a specified direction within a unit solid angle. When the light source radiates uniformly, the light intensity is I = f/ω; , omega; Is the solid angle, with the unit of sphericity (sr), F is the luminous flux, with the unit of lumen, and I=F/4 is the point light source. Brightness refers to the brightness of the light-emitting surface, which refers to the ratio of the luminous intensity of the light-emitting surface in the specified direction to the area of the light-emitting surface perpendicular to the specified direction, and the unit is candela per square meter. For diffuse reflection surfaces, although the light intensity and luminous flux in all directions are different, the brightness in all directions is equal. The screen of a TV is similar to such a diffuse surface, so when you look at the image from all directions, you will have the same brightness. The following are the brightness values of some light sources: unit CD/msup 2；; Sun:1.5 *10; Fluorescent lamp: (5 mdash10) *10supp3; ; Moonlight (full moon): 2.5 *10supp3; ; Black and white TV screen: about120; Color TV screen: about 80. 3. The luminous flux and light energy emitted by lumen light source radiate in all directions, and the light energy passing through a certain area in unit time is called the radiant energy flux passing through the area. The sensitivity of eyes to different colors of light varies with frequency. Even if the radiant energy flux of different colors of light is equal, it cannot produce the same brightness visually. Among all colors of light, yellow and green light can cause the feeling of brightness most. If green light is taken as the standard, its luminous flux is equal to radiant energy flux. For other colors of light, the ability to arouse brightness is less than green light, and the luminous flux is also less than radiant energy flux. The unit of luminous flux is lumen, which is the transliteration of English lumen, abbreviated as lm. At the solidification temperature of platinum, the absolute blackbody ranges from 5.305 *10supp3; Cmsup2 The luminous flux radiated in this area is 1lm. In order to show the relationship between light intensity and luminous flux, a point light source with light intensity of 1 Candeira emits luminous flux of 1 lumen in unit solid angle (1 sphericity). The output luminous flux of 40W fluorescent lamp is about 2 100 lumens. 4. The illuminance and lux illuminance can be directly measured by an illuminance meter. The unit of illumination is lux, which is a transliteration of English lux and can also be written as lx. When the light flux of the illuminated object is 1 lumen in the area of 1 square meter, its illuminance is 1 lux. Sometimes, in order to make full use of the light source, a reflective device is often attached to the light source, so that more luminous flux can be obtained in some directions to increase the illumination on the illuminated surface. Such as car headlights, flashlight, photographic lamp, etc. The following are various ambient illumination values: lux night: 0.001mdash; 0.02; Moonlight night: 0.02mdash0.3; Indoor cloudy: 5mdash50; Outdoor on cloudy days: 50mdash500; Indoor in sunny days:100 mdash; 1000; Illuminance under midday sunlight in summer: about 10*9 power; Illumination required for reading books and periodicals: 50mdash60; Standard illuminance of home camera: 1400.