*Units: lumens/steradian (lm/sr), equivalent to candela (cd) The candela is an SI unit defined as the luminous intensity in a given direction of a source that emits monochromatic radiation of frequency 540 x 10 12 Hz (equivalent to a wavelength of 555 nm) and that has a radiant intensity in that direction of (1/683) watt per steradian

Luminous efficacy measures how effectively the eye converts radiant flux into a visual sensation. Luminous efficacy of a source is the ratio of output luminous flux (lm) to input electrical power (W). Luminous efficacy of a radiation is the ratio of luminous flux (lm) to radiant power (W), and is therefore the theoretical maximum that a light source with a given spectral distribution can achieve with 100% radiant efficiency.
* Units: lumens/watt (lm/W)

Luminance is the density of the luminous flux incident on a surface. Its value is determined by luminous intensity, angle of incidence and distance from the source to the surface.
* Units: lumen/square meter (lm/m 2 ), equivalent to lux.
* Alternative unit: foot-candle, equivalent to lumen/foot 2 . To convert from foot-candle to lux, multiply by 10.76

Luminance is the luminous intensity per unit emitting area for a non-point source. To the observer, the property of luminance corresponds to the brightness of the source.
* Units: candela/square meter (cd/m 2 ), equivalent to nit

.

Warm color: < 3300K

Medium color: 3300 to 5000K

Daylight color: 5000K to 6500K

Cool color: > 6500K

Even if light color is the same with, among the kinds of light maybe cause it's big difference on Color rendering . Since it's send out different of spectrum.

Thought generally the man-made light source should let the human eye correctly sensation color, the like under the sunlight looked the thing is same. Certainly this must regard situation of and the goal the application has the different request degree. This according to is the light source color rendering, called it general color rendering index, (Ra) If general color rendering index for the thing under some light source illumination color of the demonstration under the reference light source illumination color both the relative difference. Evaluation law its value refers to the light source for the distinction and waits the light measuring source according to on kind to make the comparison and quantification its difference one by one in DIN 6169 stipulation eighth; The difference is smaller, namely representative waits the light measuring source to color rending to be better, color rending index Ra is equally 100 light source may let each kind of color present the like to refer to color of the light source illumination. The ether sunlight color rending in the nature to be best, therefore, the spectrum closer sunlight artificial light source , it color rending to be better.

The electromagnetic spectrum consists of all the different wavelengths of electromagnetic radiation, including light, radio waves and x-rays. It is a continuum of wavelengths, from zero to infinity. We name regions of the spectrum rather arbitrarily, but the names give us a general sense of the energy; for example, ultraviolet light has shorter wavelengths than radio light. The only region in the entire electromagnetic spectrum that our eyes are sensitive to is the visible region.

Gamma rays have the shortest wavelengths, < 0.001 mm(about the size of an atomic nucleus). This is the highest frequency and most energetic region of the electromagnetic spectrum. Gamma rays can result from nuclear reactions taking place in objects such as pulsars, quasars, and black holes.

X-rays Range in wavelength from 0.001 - 10 nm (about the size of an atom). They are generated, for example, by superheated gas from exploding stars and quasars, where temperatures are near a million to ten million degrees.

Ultraviolet radiation has wavelengths of 10 - 400 nm (about the size of a virus). Young, hot stars produce a lot of ultraviolet light and bathe interstellar space with this energetic light.

Visible light


Cover the range of wavelengths from 400 - 700 nm (from the size of a molecule to a protozoan). Our sun emits the most of its radiation in the visible range, which our eyes perceive as the colors of the rainbow. Our eyes are sensitive only to this small portion of the electromagnetic spectrum.

Infrared wavelengths span from 700 nm - 1 mm (from the width of a pinpoint to the size of small plant seeds). At a temperature of 37 degrees C, our bodies radiate with peak intensity near 900 nm.

Radio waves are longer than 1 mm. Since these are the longest waves, they have the lowest energy and are associated with the lowest temperatures. Radio wavelengths are found everywhere: in the background radiation of the universe, in interstellar clouds, and in the cool remnants supernova explosions, to name a few. Radio stations use radio wavelengths of electromagnetic radiation to send signals that our radios then translate into sound. These wavelengths are typically a few feet long in the FM band and up to 300 yards or more in the AM band. Radio stations transmit electromagnetic radiation, not sound. The radio station encodes a pattern on the electromagnetic radiation it transmits, and then our radios receive the electromagnetic radiation, decode the pattern and translate the pattern into sound.

goto top