Glensman Posted July 26, 2009 Report Share Posted July 26, 2009 Hi Lads, I recently got given some 24v 250 Watt bulbs that would be suitable for a lamp- so this got me thinking that I may make a high powered lamp for myself, but before I go to the bother I was wondering just how powerful would one of these bulbs be, say in comparison to my Lightforce 240 Blitz?? Quote Link to comment Share on other sites More sharing options...
pigeon master Posted July 26, 2009 Report Share Posted July 26, 2009 Candlepower is a rating of light output at the source, using English measurements. Foot-candles are a measurement of light at an illuminated object. Lumens are a metric equivalent to foot-candles in that they are measured at an object you want to illuminate. Divide the number of lumens you have produced, or are capable of producing, by 12.57 and you get the candlepower equivalent of that light source. It's not a simple factor. The first complication is that candle power and watts aren't the same thing expressed in different units. The second, and major complication, is that candle power (and the other variables of photometry) involve only energy that is visible to the human eye. Watts and lumens are similar units, watts being a measure of radiant energy flux, lumens being a measure of only the visible part of radiant energy flux. Watts are also a measure of power (volts x amperes) input into an electric lamp. I notice that physicists seem to avoid using the term "candlepower", but I'm taking the unit of candle power to be the candle and 1 candle is 1 lumen per sterradian. (A steradian is a measure of solid angle; for example, the size of a flashlight beam in two dimensions - up/down and left/right. There are 12.57 steradians in a sphere, and since 1 radian=57.3 degrees, there are about 3283 square degrees per steradian.) Thus, a flashlight which produces 10 lumens spread out over a 60 degree round beam is a 10 candle light, probably termed a 10 candlepower light by engineers. On the other hand, a flashlight which produces the same 10 lumens concentrated in a 6 degree beam is a 1000 candle light. From what I read, ordinary small incandescent bulbs can produce about 8 or 10 lumens per watt of input power. Losses are heat and invisible infrared energy, so obviously watts and lumens are scaled very differently - in other words, a lossless source of light would produce many lumens (as many as 683?) for each watt of input. You could do some sums but you'll need much more information to determine if a 250 watt bulb is anywhere close to a purpose built lamp. The PM Quote Link to comment Share on other sites More sharing options...
Glensman Posted July 26, 2009 Author Report Share Posted July 26, 2009 Makes sense... and thanks for the detail, you've answered a good few questions that I've wondered about. One of the things I take from your answer is that the lamp (reflective area) are as important as the bulb... I'm wondering does anyone else have any experience of this to give me an idea of whether or not to bother?.. Quote Link to comment Share on other sites More sharing options...
ryantidgwell Posted July 26, 2009 Report Share Posted July 26, 2009 all u can do is try it just get some tubing stick the bulb in it at night and see how bright it is , Quote Link to comment Share on other sites More sharing options...
digit Posted July 26, 2009 Report Share Posted July 26, 2009 You've got to think of the weight of two 12 volt batteries, and 250 watt bulbs a going to use a lot of power Quote Link to comment Share on other sites More sharing options...
Glensman Posted July 26, 2009 Author Report Share Posted July 26, 2009 well I was thinking of rigging up car batteries on a very long lead and they could sit in the car... I'm certainly not planning on walking about with it. Quote Link to comment Share on other sites More sharing options...
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