Beam spread is the angle of the light beam measured between two points on a polar distribution curve at the point where the luminous intensity drops to half its maximum value.

Illuminance (abbreviation: E) with the unit of measure lux (lx) specifies the luminous flux (measured in lumens: lm) that is emitted onto a specific surface from a light source: this consists of one lux when the luminous flux of one lumen homogeneously illuminates one square metre of surface.

False colour rendering is used in lighting calculations to clarify the various illuminance levels on specific furniture and surfaces. By displaying the scene in bold colours, the fine differences of lighting on furniture, goods, merchandise fixtures and walls can be clearly differentiated between.

The colour temperature is the temperature at which a thermal radiator emits light of a colour similar to that of the light source. Colour temperature is measured in degrees Kelvin.
Herewith one can differentiate between warm white (ww, <3300K), neutral white (nw, 3300-5000K) and daylight white (tw, >5000K).

A lamp‘s colour reproduction attributes are characterised by the general colour rendering index (Ra). The colour reproduction of a light source is described by using an incandescent lamp with the same colour temperature as a reference. It is assumed that lamps with an Ra value of >_ 90 provide optimal colour rendering.

Rated lamp life is defined as the time after which 50% of the lamps in a lighting system have failed.

Eine licht-emittierende Diode (LED) ist ein Halbleiterbauelement, das inkohärentes Licht in einem engen Spektralbereich emittiert, wenn es in Vorwärtsrichtung elektrisch betrieben wird.

Power consumption is the electrical energy in Watts (W) consumed by a lamp or a ballast.

Luminance (L) is a measure of the subjective brightness of a luminous or illuminated surface as perceived by the human eye. It is measured in candela per square meters (cd/m²).

Luminous efficacy describes a lamp‘s efficiency and is measured in lumens per watt (lm/W). The higher the lm/W ratio, the more efficient the lamp is.

Luminous intensity (l) is the lumen output emitted by a light source per unit solid angle in a specific direction. It is measured in candelas (cd).

Lumen output is the total emitted light power of a light source. It describes the visible light radiating from a light source in all directions. It is measured in lumens (lm).

Lumen is the SI unit for luminous flux. A lumen is the luminous flux emitted from a point-formed light source within a standard angle of 1 steradian and that has a homogeneous luminous intensity of one candela. A steradian is a standardised angle of unity in three dimensions.

Lux is the SI unit for illuminance, and its unit of designation is 'lx'. One lux is equivalent to the luminous flux of one lumen upon one square metre of surface: 1 lx = 1lm / m².

“Economic lamp life“ is based on average lamp failures and the falloff in the lumen output emitted by the individual lamps in the lighting system. It is defined as the point in time when the overall system‘s luminous intensity has dropped to 80%.

Reflectance or reflectivity is the ratio between reflected and incident lumen output. Bright surfaces have high reflectance, dark surfaces have low reflectance.