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 Topic: what's a lux?
Posted: December 05 2005 at 1:10am |
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Is there anyone out there that can explain to me what a lux is? It's not the same as Kelvin, is it?
Edited by Amie - January 10 2008 at 3:00am
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Adam Haycock
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Posted: December 05 2005 at 1:35am |
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Mark Peterson
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Posted: December 05 2005 at 8:48am |
This is a very important topic and it should be moved to the Lighting section.
We also need to discuss Lumens and Color Rendering Index (CRI)
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jfinch
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Posted: December 05 2005 at 9:06am |
And most importantly... PAR.
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Posted: December 05 2005 at 9:25am |
 Mark Peterson wrote:
This is a very important topic and it should be moved to the Lighting section.
We also need to discuss Lumens and Color Rendering Index (CRI)
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I knew someone was going to say that. I put it in this section because I am trying to build something that is not fish related. I am trying to design a light box for someone that has Seasonal Affected Disorder (SAD). The person is suppose to sit 20" away from lights that are 10,000 lux for 20 minutes a day. Is there someway to measure the lux of a light at a given distance?
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Adam Blundell
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Posted: December 05 2005 at 9:32am |
Amie-
I have a lux meter you can borrow. Let me find it....
Adam
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jfinch
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Posted: December 05 2005 at 9:33am |
Is there someway to measure the lux of a light at a given distance?
Yes. Get or borrow a lux meter (photographers use them). A 250 W MH bulb has an intensity of about 24,000 lumen. Spread all that light out over 2 meters and you would have 12,000 lux.
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Posted: December 05 2005 at 9:48am |
Adam Blundell wrote:
Amie-
I have a lux meter you can borrow. Let me find it....
Adam
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Fantastic! Thanks.
JFinch wrote:
Amie-A 250 W MH bulb has an intensity of about 24,000 lumen. Spread all that light out over 2 meters and you would have 12,000 lux. |
Sounds like a good reason to get a MH on my tank.  Seriously though, is there a distance that you could sit from your tank and the lux would be 10,000? I guess the hood of the tank would have to be up, right? Would a 125 W MH mean that you would only have to be 1 meter away to get 11,000 lux?
Edited by Amie
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Adam Haycock
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Posted: December 05 2005 at 3:26pm |
Amie, does it say anything about what color of light to use? Id would think a 6500K metal halide would be perfect for that. Hmm maybe a good excuse to buy a pendant for a new frag tank ;)
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bbeck4x4
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Posted: December 05 2005 at 10:27pm |
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we have a box that is supposed to be used for SAD it has two 65 watt f40bx/spx41/rs bulbs in it, that would be a 4100 k bulbs
Brian
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Posted: December 06 2005 at 12:46am |
Adam Haycock wrote:
Amie, does it say anything about what color of light to use? Id would think a 6500K metal halide would be perfect for that. Hmm maybe a good excuse to buy a pendant for a new frag tank ;)
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The only information I have been able to find states that the light needs to be 10,000 lux at 12", properly screen out UV wavelengths, and preferably have a broad spectrum of color. ( I guess the color doesn't matter as much.) I think the idea is to simulate sunlight.
Is a 6500 K light 'whiter' or more yellow than a 10,000 K light?
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faviasteve
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Posted: December 06 2005 at 1:10am |
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6500 K is more yellow than 10,000K so it isn't as pretty on a reef tank but the the Iwasaki 6500 K simutates natural sunlight at the surface better than any other metal halide so it should be a super SAD bulb. Anything between 4000 K and 10000 K is probably OK.
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Steve Burton
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Posted: December 06 2005 at 11:40am |
bbeck4x4 wrote:
we have a box that is supposed to be used for SAD it has two 65 watt f40bx/spx41/rs bulbs in it, that would be a 4100 k bulbs
Brian
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Are you using it? Do you want to sell it?
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bbeck4x4
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Posted: December 06 2005 at 6:18pm |
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we are using it with a timer to have the daylight (simulated) occur at
6:00 am, so far its working pretty good, I was having trouble with
staying asleep at night.
Brian
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Posted: December 12 2005 at 11:16am |
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Thanks to Adam letting me borrow his lux meter, I was able to test different lights. I found that a 55 Watt 10,000K power compact emits 10000 lux at 20 inches. Now I just need to figure out the UV issues and I'm set. I assume that I can just get a piece of UV protective glass from a glass company?
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Adam Blundell
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Posted: December 12 2005 at 11:19am |
Yes, but I would get a piece wide enough to cover two bulbs. After using that glass you will lose a lot of your light and may need to use two 55 watt bulbs.
JON- do you think you need to filter UV light from pc bulbs? I don't.
Adam
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jfinch
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Posted: December 12 2005 at 11:35am |
do you think you need to filter UV light from pc bulbs? I don't.
I doubt it too. I'd use the bulbs as is.
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Posted: December 12 2005 at 11:38am |
Adam Blundell wrote:
JON- do you think you need to filter UV light from pc bulbs? I don't.
Adam
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You are right, Adam... I went back and reread the article you sent me on UV Radiation (http://www.advancedaquarist.com/issues/aug2004/feature.htm) and I don't need to worry about Power Compacts unless the total wattage is above 400.
Thanks for ALL your help!
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