Indoor Furnishings User Manual

23
2000-11-07
Colour rendering
Effect of an illuminant on the colour appearance of objects by conscious or subconscious comparison
with their colour appearance under a reference illuminant.
Colour rendering Measure of the degree to which the psychophysical colour of an object illuminated by the test
index (R) illuminant conforms to that of the same object illuminated by the reference illuminant,suitable
allowance having been made for the state of chromatic adaptation.
Colour rendering Mean of the CIE 1974 special colour rendering indices for a specified set of eight test colour samples.
index,CIE 1974
general (R
a
)
Colour temperature
The temperature of a Planckian radiator whose radiation has the same chromaticity as that of a given
stimulus.
It is expressed in kelvin (K).
Colour temperature, The temperature of the Planckian radiator whose perceived colour most closely resembles that of a
correlated given stimulus at the same brightness and under specified viewing conditions.
It is expressed in kelvin (K).
Illuminance (at a point of a surface).Quotient of the luminous flux incident on an element of the surface containing
the point,by the area of that element.
It is expressed in lux (lx) = lumen per square metre (lm/m
2
).
Life, rated average The number of burning hours on average, after which 50% of large representative groups of lamps in
laboratory tests,under controlled burning conditions and at a specified number of burning hours per
start, have failed.
The correct term should be “median” life, as it defines the 50% mortality point and not necessarily the
average of all individual technical lamp lives.Nevertheless this lifetime indication is used by all American
companies (and also by Philips),whereby the switching cycle is based on a specific number of hours per
start.
Luminance (in a given direction,at a given point of a real or imaginary surface). Quantity defined by the formula,
where the luminous flux is transmitted by an elementary beam passing through the given point and
propagating in the solid angle containing the given direction; the area of a section of that beam
containing the given point;the angle between the normal to that section and the direction of the beam.
It is expressed in candela per square metre (cd/m
2
).
Luminous efficacy (of a source).Quotient of the luminous flux emitted by the power consumed by the source.
It is expressed in lumen per watt (lm/W).
Luminous flux Quantity derived from radiant flux by evaluating the radiation according to its action upon the
CIE standard photometric observer.
It is expressed in lumen (lm).
Luminous intensity (of a source in a given direction).Quotient of the luminous flux leaving the source and propagated in
the element of solid angle containing the given direction,by the element of solid angle.
It is expressed in candela (cd).
Luminous intensity Distribution of the luminous intensities of a lamp or luminaire in all spatial directions.
distribution
Lighting definitions
6. Definitions