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100 plus 100 = 200

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Calum Guthrie
100 plus 100 = 200
on Jul 31, 2009 at 8:25:55 pm

I'm curious. I'm by no means a lighting man. I'm a no budget person, making my own light boxes. I have a 750watt generator, so all my bulbs are florescent. To reach further, or light a greater space, I would need a more powerful bulb. But if I made a box with two bulbs of say 100w would it be the equivalent of a 200w bulb?

Also the max florescent bulb I've seen is 200W for around £50 (http://bmz2.all4sourcing.com/d/d366f7be0b2687d9014461fe059ea0a1.image.400x400.jpgsaw a £28 pound plant light of the same but after delivery it was the same), in the UK. Is this correct?


sto pro veritate


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Bill Davis
Re: 100 plus 100 = 200
on Aug 4, 2009 at 3:02:12 am

Well - yes, it would be "equivalent." But that's not really the issue.

You note you're attempting to achieve "reach" with the light. Light, like sound, is a wave phenomena that generally follows the inverse square principal.

Double the distance from source to illuminated object and the light falloff is 4 times. Triple the distance and the falloff is 9 times. Move from 1 foot distant to 10 feet distant and the drop off is 100 times.

So while doubling the output of the fixture will net you twice the illumination at 10 feet - that will be 2 100ths of the original value. Or not much extra light.

To project light at distance, a fluorescent array is a marginal choice at best. A fresnel lens is MUCH better. An ellipsoidal lens is better yet. Which you choose is dependent on the quality of the light you wish to project - whether you seek softer or harder edged illumination.

Good luck.



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