Thread: T5 lightings
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Old 09-10-2006, 11:21 PM   #54
BarraCuda™
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Quote:
Originally Posted by aropal View Post
If you are looking at a light that is described in terms of its lumen output then you have no basis for making disparaging comments in terms of its lux.
Dont take my word for it. Ask the manufacturer for the lux rating. See if that particular light fixture is made for spot lumination.

Quote:
Originally Posted by aropal
The primary implementation of led lighting is that each element produces a small amount of light and then focuses it to a specific location. If you want more distributed light then you use more elements focussed on different areas.. If you want more intense light then you focus more elements on THE SAME area.
I agree with that. So you will need alot of narrow beam LEDs to luminate the entire tank right?

Quote:
Originally Posted by aropal
How is this relevant. All we care about is how many lumens are produced per watt.
Basic DC electrical theory tells you that Power(watt) = Voltage x Amperes
Assuming constant current, a higher voltage will give you higher wattage and a brighter bulb!

Quote:
Originally Posted by aropal
In terms of keeping fish, plants and invertebrates we might also reasonable be interested in CRI such that the action spectrum of our captive organisms are catered for.

[Incidentally, there are numerous bright LED manufacturers which claim a CRI in excess of 80; the only questions remaining are with regard to the location in the spectrum of that missing 20%]
CRI only tells you the difference between the colors viewed under sunlight and under the bulb. If the CRI is 100 then the color you look under the bulb will be 100% the same as you would have under the sun.

LEDs are not like FL or MH as it only have a very narrow spectrum. Ask for the spectrum chart of any single LED and you will see that the output will peak at a very narrow spectrum.

CRI = Color Rendering Index, nothing to do with spectrum quality needed for plants.
http://en.wikipedia.org/wiki/Color_rendering_index

What you should be looking at is Photosynthetically Usable Radiation (PUR) Plants typically require a peak at spectrum ~620-700nm for photosynthesis and other wavelength of light to survive. In order to create such a wide spectrum then multiple LEDs peaking at different wavelength would have to be mixed, look uniformed and pleasing to the eyes. Its easier said then done


Quote:
Originally Posted by aropal
The area covered is not 1cm x 1cm. Each of the three led elements is itself 1cm x 1cm. There are numerous brands of Luxeon led with differing beam angles I believe there are 10, 25 and 30 degree angles available.

You have insisted upon many facts in this thread which have been baseless or wildly inaccurate from the claimed 55 lumens for 3 watts maximum to the 1cm squared beam spread. Posting inaccurate and unsupported data is unhelpful to anyone.
I'm only stating an example for the 1000 lumens at 1cm X 1cm spot. It is to illustrate my point that its worthless to have such brightness when the area covered is just a small spot. You will need still alot of them to cover the entire tank.

Again dont take my words for it, ask the manufacturer for specifications. I can sum things up for you now.

No, 1 watt LEDs cannot produce 170 lumens as of today's technology.
High lumens LEDs are highly focused and not suitable for lighting wide areas.
Wide angle LEDs are dim and do not have power to penetrate deep tanks.
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