Luminous Flux

Luminous Flux is the measure of the perceived power of light and is adjusted to reflect the varying sensitivity of the human eye to different wavelengths of light. The unit of luminous flux is the lumen (lm). One lumen is defined as the luminous flux of light produced by a light source that emits one candela of luminous intensity over a solid angle of one steradian.
 
 
Luminous Intensity

Luminous intensity is a measure of the wavelength-weighted power emitted by a light source in a particular direction per unit solid angle, based on the luminosity function, a standardized model of the sensitivity of the human eye. The unit of luminous intensity is the candela (cd),
 
 
Illuminance

Illuminance is the total luminous flux incident on a surface, per unit area. It is a measure of the intensity of the incident light, wavelength-weighted by the luminosity function to correlate with human brightness perception. The unit of illuminance is lux (lx).

Luminous Efficacy

Luminous efficacy is a measure of how well a light source produces visible light. It is the ratio of luminous flux to power. The unit of luminous efficacy is lm/W.

   
Color Temperature

Color temperature is a characteristic of visible light that has important applications in lighting, photography, videography, publishing, manufacturing, astrophysics, and other fields. The color temperature of a light source is the temperature of an ideal black-body radiator that radiates light of comparable hue to that of the light source. Color temperature is conventionally stated in the unit of absolute temperature, the kelvin (K).
 

Color Rendering Index

The color rendering index (CRI) is a quantitative measure of the ability of a light source to reproduce the colors of various objects faithfully in comparison with an ideal or natural light source. Light sources with a high CRI are desirable in color-critical applications such as photography and cinematography.
 

Luminaire Efficiency

Luminaire efficiency is the ratio of light output emitted by the luminaire to the light output emitted by its lamps. Luminaire efficiency is the percentage of light output produced by the lamps that are in turn emitted by the luminaire.

    

Spectrum

Spectrum is referring to the range of colors observed when white light was dispersed through a prism.

 

Glare

Glare is caused by a significant ratio of luminance between the task (that which is being looked at) and the glare source. Factors such as the angle between the task and the glare source and eye adaptation have significant impacts on the experience of glare.

    

Unified Glare Rating

Unified Glare Rating(UGR) is an international index presented by CIE and is used to evaluate and limit the psychological direct glare from luminaires.

   
 

Light Intensity Distribution

The spatial distribution of the light intensity of a light source results in a three-dimensional body of light intensity distribution. A section through this light intensity body will give the light intensity distribution curve, which describes the light intensity distribution in one plane.

   

Uniformity of Illumination

Uniformity of illumination of a given plane is calculated as the quotient of the lowest value for the illuminance of the plane and the average illuminance of that plane.

    
 
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