ADA Signage: Americans with Disabilities Act (e.g. Tactile signs with Braille)
Ambient light: spill from existing light sources
Afterglow: emission of light after a source of excitation energy is removed, usually by phosphorescence
Candela: unit of luminous intensity
Charging: excitation of a phosphorescent material, usually by incident light
Daylight fluorescence (DF): fluorescence where the emission is in the visible spectrum
DIN67510 Part 1: specification describing afterglow performance in a standard way, in the form a/b - c - d - e, where a is afterglow brightness in mcd/m2 after ten minutes, b is afterglow brightness after sixty minutes, c is the decay period in minutes to 0.3 mcd/m², d is excitation color code, e is emission color code. Parts 2 and 3 refer to in situ testing of photoluminescent items.
Excited state: condition of a charged phosphor before emission
Electroluminescence (EL): luminescence where the initial energy comes from electric fields, usually alternating
Fluorescence: very fast absorption and emission of photons where there is no appreciable afterglow
Flux (light): luminous intensity, usually of a light source, per unit solid angle; unit: lumen
Illuminant A, B, C: incandescent illumination in the range 380nm to 770nm, respectively 2856K (yellow), 4874K (mean noon sunlight) and 6774K (average daylight, blue)
Illuminant D: daylight illuminants defined from 300-830nm, designated with a two digit subscript to describe Correlated Color Temperature, e.g. D65 indicates 6500K, close to Illuminant C
Illumination: luminous flux, usually of incident light. Units: lux or lumens per square meter
Infrared: part of the electromagnet spectrum immediately less energetic than visible light, ranging from around 700 nanometers to 10 microns wavelength
Lumen: unit of light flux. One lumen per square meter is one lux. One lumen per square foot is one foot-candle. Lux is the illuminance equal to one lumen per square meter.
Luminance: brightness, usually of a surface, i.e. luminous intensity per unit area. unit: candelas per square meter, usually expressed in millicandelas per square meter.
Luminescence: emission of light from a substance unaccompanied by heat
Luminous directional reflectance: reflectance of a surface in given directions of illumination and view. The ratio of the brightness of a surface to the brightness that an ideally diffusing, perfectly white surface would have if illuminated in the same way. Units: none
Luminous intensity: a fundamental unit derived from black body radiation at set conditions in a given direction. Unit: candela
Luminous efficiency (L): luminous flux emitted by a source, per unit of power consumed; unit: lumens per Watt
Lux: unit of illuminance, lumens per square metre; in imperial units, one footcandle is approximately 10 lux
mcd/m² : The performance of luminescent signs and markings, which is a property of the materials from which they are fabricated, is measured in the (metric) units of millicandela per square meter.
Phosphor: a substance exhibiting the property of phosphorescence
Phosphorescence: slower absorption and emission of photons where afterglow is usually apparent
Photoluminescence: luminescence where the energy comes from incident light; includes fluorescent and phosphorescent processes
Saturation: charging of a phosphorescent material to maximum
Ultraviolet: part of the electromagnet spectrum immediately more energetic than visible light, ranging from approx. 100 nanometers (VUV) to 400 nanometers (UVA) wavelength.