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Lumen (symbol: LM) SI derived unit is a measure of the total amount of luminous flux emitted by the visible light source. The luminous flux is different from power (radian flux), which contains all emitted electromagnetic waves, while the luminous flux is weighted according to a model of a sensitivity of the human eye to various wavelengths (a "luminance function"). With a lux of lumens about one lux per square meter being lumens.

1 lm = 1 cd ⋅ sr.

A solid angle of a full sphere has a steradiance 4π, so that a light source emitting a homogeneous light has a total luminous flux in all directions 4π r = 4π cd⋅sr ≈ 12.57 lumen x 1 cd.

Lumen Tests

A light source, one emitting diam equal to one solid power of light intensity along one steradian, total luminous flux emitted from this angle, a lumen (1 cd · 1 sr = 1 lm). Alternatively, an isotropic single candela light source emits a total luminous flux of 4 lumens exactly. If the welding is partially covered by an ideal absorbent hemisphere, that system emits the half-light flux (2π lumens only). The light intensity will still be a candela in the direction that has not been concealed.

The lumen may be considered as a measure of the total "amount" of visible light at a defined beam or angle, or emitted from a source. The number of candelas or lumens from a source also depends on the spectrum by means of the nominal response of the human eye represented in the luminescence function.

The difference between the lumen and the luxury units is that luxury takes into account the area where the luminous flux spreads. 1000 spans an area of ​​1000 square meters with a fluency of lumen, 1000 burns that square with a brightness of square meters. The same 1000 lumen, which spans ten square meters, provides only less illumination than 100 lux. Mathematically, 1 lx = 1 lm / m 2

A source (555 nm wavelength in the green region of the optical spectrum) that gives the power of a watt light of the color in which the eye is most efficient has the 683 lumen luminous flux. Thus, a lumen represents at least 1 / 683 watts of visible light power depending on its spectral distribution.

470 is a standard LED lamp that can produce lumens. It consumes about one-sixth of an incandescent bulb that produces the same light.

The lighting used for lamps is commonly labeled with their light output from the lumen; In many jurisdictions this is required by law.

The 23 W helical compact fluorescent lamp emits approximately 1.400-1.600 lm. Many compact fluorescent lamps and other alternative light sources are labeled as equivalent to an incandescent bulb with a given watt. Below is a table showing typical luminous flux for incandescent bulbs and their equivalents.

1 In September 2010, European Union legislation began to mandate that lighting equipment should be labeled in luminous flux (lm), rather than electric power (W). This amendment is a result of the EU's Eco Design Directive for Energy-Use Products (EuP). For example, according to the European Union standard, an energy efficient bulb claiming to be equivalent to a 60 W tungsten bulb must have a minimum 700 X 750 lm light output.

ANSI lumens

The light output of projectors (including video projectors) is typically measured in lumens. A standardized procedure for testing the projectors was established by the American National Standards Institute by combining various measurements taken at different positions. For marketing purposes, the luminous flux of the projectors tested according to this procedure may be quoted with "ANSI lumens" to distinguish them from those tested by other methods. ANSI lumen measurements are generally more accurate than other measurement techniques used in the projector industry. This makes it easier to compare the projectors' brightness characteristics.

The method for measuring ANSI lumens is defined in the IT1992 document created in 7.215. First, the projector is set to display an image in a room at 25 degrees Celsius. The brightness and contrast of the projector are adjusted to distinguish between the% 95 peak white% 5 display area block and the% 100 and% 90 peak white boxes of the same size in the center in an all-white area. The light output of the white area is then measured and averaged in a full white area at nine specific points around the screen. This average is then multiplied by the display area to give the brightness of the projector in the "ANSI lumen".

Peak lumen

Peak lumens are a measure of the light output normally used with CRT video projectors. The test uses a test pattern, typically white on the percent 10 and 20 of the display area, white in the center of the screen and black on the rest. The light output is measured only in this central area. Limitations with CRT video projectors cause them to produce more brightness when only part of the image content is at the highest brightness. For example, the Sony VPH-G70Q CRT video projector produces 1200 "peak" lumens but only produces 200 ANSI lumens.

Colorful light output

Brightness (white light output) measures the total amount of light projected in the lumens. Color brightness specification The Color Light Output measures red, green, and blue on a nine-point grid, each using the same approach used to measure brightness. Experts advise projector buyers to have equal white light output and color light output for the best viewing experience.

You can work with our laboratory EUROLAB for lumen testing.