XP-G's versus Luxeon LED's

Before I drop my weeks work on some aquarium lighting I'm hoping some of you would shed some lighting on the contrasts between
XP-G's by Rapid LED Home Page versus Luxeon Stars by Luxeon Star High Power LEDs

It would be very helpful to have some information of someone who actually knows lighting unlike myself before I make the leap forward using my flux machine to upgrade my lighting from T5's to LED's.

Both Rapid LED Home Page and Steve's LED's Home Page offer very interesting offers for the Biocube Kits utilizing the hood for moonlighting, day and actinic lighting, as well as fans and dimmable controls.

They are roughly in the same ball park as far as prices go -- just curious to see which lighting would offer the best PAR readings for my tank

(Personally I feel the Luxeon Stars are newer and more powerful, but again I have no experience or knowledge on LEDs or reef tank lighting for that
matter)

Thank you to all who post!!

 

Bumpity bump bump

 

I no nothing really about Luxeon LEDs, but Im interested. Shameless bump. Hopefully someone with some information can chime in.

 

If you looked at data sheets for the cool whites those LED's provide roughly the same amount of light. Luxeon 320 lumens at 1A, Cree XP-G R5 348 at 1A. I doubt you will be able to see a difference using just human eyes. As far as Royal Blue goes, Steve correctly notes that the Luxeon (where's the data sheet for the RB?) is superior to the Cree since it outputs 1200mW of light vs Cree XP-E's ~900mW at 1A. You should not drive the XP-Es that high though, as that's their max. On a biocube though, with such small numbers, I don't know if it will be that significant. Those kits are significantly different in the drivers and heatsinks these sellers provide. So decide more on that. The LED debate is Coke vs. Pepsi at this point.

 

Sorry, but what do lumens have to do with the amount of light? Lumens are a measure of luminous flux and have nothing to do with the amount light only the perceived amount of light by the human eye.

If we look at the photopic luminosity curve (in black), 550nm "yellow-green" light is given 20x the weight of the same amount of 450nm "blue" light for example! So, all your telling me is the Luxeon has more yellow-green light, which by the way is likely pretty useless for photosynthesis with regards to our corals. We live in a PAR world, not a lumen world, I know you don't have PAR numbers available, I don't either, which is why I can't comment, but talking in lumens as a surrogate is just deceptive... As of now, I don't think anyone can answer the question unfortunately...

 

pwreef, by the way, I apologize if I sound blunt. I don't mean to flame you, but this lumen junk is all over the web, and nevertheless is completely useless to us. So, it appears the weighting of lumens needs to be emphasized better. If you had 1 blue led and 1 green-yellow led, the green-yellow could easily have around 20x the output if measured by lumens, but the same PAR and less PUR. PUR is what we are really interested in, but we don't necessarily know enough about photosynthetic responses in corals to accurately define it. However, PAR works reasonably good. Lumens are not even slightly good.

 

I am aware of the PAR and PUR issues. Lumens have nothing to do with photosythesis. They have something to do with comparing sources of light. Well at least this is what people in the lighting industry seem to use. The OP is asking to compare two LED emitters. Unless someone builds two identical fixtures, puts them over water and measures PAR on each one there is no way to tell which LED emitter is better. On RC you can even find discussions about how the PAR metering is not a great measure either because LEDs emit a narrow spectrum. So the data sheets show us measured intensity of each emitter at a given current and FOR GIVEN SPECTRUM. Comparing yellow and blue LEDs is useless. Comparing LEDs of the same wavelegth gives us something. With all that said more people are growing corals under Cree LEDs it seems, so that is a 'proven' emitter. Luxeon might be just as good for corals. I am kinda new to all this, but the longer I am in the hobby the longer I get an impression that most of the things we do are just a giant experiment. Sometimes things work by the book and other times even the experts in the field are scratching their heads as to why corals or fish die. We try to play God too often. Happy reefing!

 

Thanks everyone this has been an interesting debate. I'm probably going to go ahead and order the retrofit kit from steve's led's with the 12 RB and 8 CW but also I've inquired about adding some variety as well. I'd be really nice during dinner time to alternate lights between red, cyan, green, and UV. Especially with dimable controls at my finger tips sounds all too exciting. Again thank you for the posts, I'm still trying to understand the differences between PAR and PUR. Understanding light and what's needed to photosynthesis is definitely difficult especially without having a PhD in Biology with a focus in lighting.

pwreef put it in a way that I agree with, so much of the things we are doing seems like a giant experianment or throwing darts with a blindfold on. Do your research, provide stability and structure, and hope for the best!

Really look forward however to replacing my PC's with LEDs, and I think my corals are looking forward to it as well