Luminous flux or luminous power is the measure of the perceived power of light. On the other hand, radiant flux is the measure of the total power of light emitted, without regard to the sensitivity of the human eye. Prism splitting light Light is electromagnetic radiation with a wavelength that is visible to the eye (visible light) or, in a technical or scientific setting, electromagnetic radiation of any wavelength. ... This article refers to the sight organ. ...

However, luminous flux is not a direct measure of the perception of brightness. PSYCHOLOGY In psychology and the cognitive sciences, perception is the process of acquiring, interpreting, selecting, and organizing sensory information. ... Brightness is an attribute of visual perception in which a source appears to emit a given amount of light. ...

Units

Any unit of power can be used to express luminous flux, however the SI unit of luminous flux is the lumen (lm) and not the watt. Jump to: navigation, search The International System of Units (abbreviated SI from the French phrase, Système International dUnités) is the most widely used system of units. ... The lumen (symbol: lm) is the SI unit of luminous flux. ... The watt (symbol: W) is the SI derived unit of power. ...

One lumen is defined as the luminous flux of light that passes from a light source of one candela through a unit steradian. Only luminous flux is expressed in lumens; radiant flux is expressed in simple watts. The candela (symbol: cd, Latin for candle) is one of the seven SI base units. ... The steradian (ste from Greek stereos, solid) is the SI derived unit of solid angle, and the 3-dimensional equivalent of the radian. ... The watt (symbol: W) is the SI derived unit of power. ...

Weighting

Different wavelengths of light are perceived as having different intensities. Thus, the luminous flux is calculated as a weighted average of the wavelengths' powers. These weighting factors are called the luminous efficacies. In statistics, given a set of data, X = { x1, x2, ..., xn} and corresponding weights, W = { w1, w2, ..., wn} the weighted mean is calculated as Note that if all the weights are equal, the weighted mean is the same as the arithmetic mean. ...

Contexts

Luminous flux is often used as an objective measure of the useful power emitted by a light source. Energy conscious consumers commonly compare the luminous flux of different light bulbs. However, luminous flux is not as useful when comparing bulbs of differing brightness, since it does not directly measure brightness. Prism splitting light Light is electromagnetic radiation with a wavelength that is visible to the eye, or in a more general sense, any electromagnetic radiation in the range from infrared to ultraviolet. ... The incandescent light bulb uses a glowing wire filament heated to white-hot by electrical resistance, to generate light (a process known as thermal radiation). ...

SI light units

<noinclude> <noinclude> luminous energy : visible radiant energy, visible light ; units are lumen*seconds or Talbots (T = lm*s) ; lumen = candela*steradian ... The second (symbol s) is a unit for time, and one of seven SI base units. ... In photometry the Talbot (T) is a nonstandard unit of luminous energy. ... The lumen (symbol: lm) is the SI unit of luminous flux. ... The steradian (ste from Greek stereos, solid) is the SI derived unit of solid angle, and the 3-dimensional equivalent of the radian. ... Luminous intensity is a measure of the energy emitted by a light source in a particular direction. ... The candela (symbol: cd, Latin for candle) is one of the seven SI base units. ... The word luminance, a synonym for luminosity, means emitting or reflecting light. ... A square metre (US spelling: square meter) is by definition the area enclosed by a square with sides each 1 metre long. ... Illuminance is the total luminous flux incident per unit area. ... The lux (symbol: lx) is the SI derived unit of illuminance or illumination. ... Luminous efficacy is a measure of the proportion of the energy supplied to a lamp that is converted into light energy. ... The watt (symbol: W) is the SI derived unit of power. ...