A.4.2 Light Density - ABB i-bus KNX Product Manual

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ABB i-bus KNX

A.4.2 Light density

© 2008 ABB STOTZ-KONTAKT GmbH
Appendix
The Light density L in cd/m
brightness which the illuminated surfaces gives to the eye.
A light density measurement device detects the reflected light, in other
words the brightness of an illuminated surface. The effect of the illumination
can only be evaluated over the light density of all surfaces in the range of
vision.
The light density of a visual object is independent of the visual distance.
The brightness does not change when the distance increases.
If white paper is subject to a lighting intensity of 500 lx, then the light density
2
is about 130-150 cd/m . At the same lighting intensity environmentally-
friendly paper has a light density of about 90-100 cd/m
The luminance is defined as follows:
L = I / A
L = light density in cd/m
I = luminous intensity in cd
2
A = surface area in m
2
(cd = Candela) is a measure of the apparent
2
2
.
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