AD 12500 Lecture Notes - Lecture 20: Incandescent Light Bulb, Light-Emitting Diode, Candlepower
20 Oct 2016
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Document Summary
Expresses (cid:498)total light output(cid:499) of a light source ( ) lumen. Property of light source, not of the object being lighted. Intensity of a light source in a particular direction. Property of source of light, not of the object being lighted: candlepower distribution curve to estimate how much light will arrive at a specific location. Footcandles: amount of light falling on a surface is measured in footcandles (fc) basic unit of illumination, one footcandle = amount of light on one square foot of surface one foot away from a candle flame. Illuminance is not a property of the light source alone; result depends upon lumens from source, distance from surface, and lightness or darkness of surrounding surfaces. Ability of a surface to reflect light. Lighter surfaces reflect more light than darker surfaces. Importance of surface reflectances: room surface reflectance is needed to obtain brightness and visual comfort, recommended: . 25 - . 45: recommended light levels for various activities.
