http://wiki.dtonline.org/index.php?action=history&feed=atom&title=LumenLumen - Revision history2026-05-29T22:23:11ZRevision history for this page on the wikiMediaWiki 1.43.8http://wiki.dtonline.org/index.php?title=Lumen&diff=5624&oldid=prevDT Online: Created article2016-03-06T20:13:09Z<p>Created article</p>
<p><b>New page</b></p><div>The total brightness of a lamp is measured in the [https://en.wikipedia.org/wiki/International_System_of_Units '''SI base unit'''] of [https://en.wikipedia.org/wiki/Candela '''Candelas'''] but for practical design purposes, it is more important to measure the amount of visible light available in a particular direction and this is measured in [https://en.wikipedia.org/wiki/Lumen_%28unit%29 '''Lumens'''].<br />
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The amount of light actually reaching a particular surface can vary according to the type of lamps used, their total wattage, their distance from the surface, and whether or not they are modified by a shade or diffuser for example. This is known as '''Illuminance''' and is measured in '''lumens per square metre''' or [https://en.wikipedia.org/wiki/Lux '''Lux'''].<br />
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For example:<br />
* a 100 watt filament bulb or its equivalent may generate 1200 lumens ''(from tables or manufacturer's information)''<br />
* it is possible that, because this lamp is shaded and positioned on a high ceiling, only 15% of its light reaches a work-surface below;<br />
* the actual light reaching the work-surface is therefore only 15% of 1200 which is 180 '''Lumens''';<br />
* assuming a standard length of kitchen worktop 3 metres long x 600mm wide ''(i.e. area = 1.8 sq.m.)'';<br />
* '''Illuminance''' ''(i.e. light arriving at the work-surface divided by its area)'' is 180 รท 1.8 = 100 '''Lumens per square metre''' or [https://en.wikipedia.org/wiki/Lux '''Lux'''].<br />
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[[Category:Terminology]]</div>DT Online