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In a message dated 95-08-03 14:16:41 EDT, you write: >+++++++++ From: Dave Drake +++++++++++++++ >I am most impressed with an American Cave Light that I'm told has a 3 hour >burn >time with a 50 W bulb. ...etc. >+++++++++ end snip ++++++++++++++++++++++++ > >My question is why are so many technical divers interested in dive >lights, WATTS. WATTS have nothing to do with bightness. > >If I remember my college physic's, light brightnes is measured in >Candle power or Lumins. If a diver what to know how bright a light >is he and/or she needs to compare the Candle Power and/or Lumin rating. > >Can someone help me out here???? Anybody with a cheap test meter can calculate the "wattage" of a bulb. To arrive at a *meaningful* value for lumen output requires very accurate measurements of voltage and current, a knowledge of colour temperature, reflector efficiency and a whole host of other things. Generally, high lumen-per-watt bulbs have a much shorter life expectancy than low l-p-w bulbs. Also the lumen output can vary dramatically with very small changes in operating voltage and will vary over the life of the bulb. Basically, quoting wattages is easier, although I agree that a lumen figure would be useful. Philip
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