Lighting and LED discussion

Discussion in 'LED Aquarium Lighting' started by gcarroll, Dec 30, 2010.

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  1. gcarroll

    gcarroll Zoanthid

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    How many people here own or have access to a PAR meter?
     
    Last edited: Jun 22, 2011
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  3. steve wright

    steve wright Super Moderator

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    I imagine very few do gcarrol

    they are expensive pieces of equipement, that you dont need very often IMO
    You check a new tube, new brand etc, and then maybe check again in a few months when it might be time to replace

    reef clubs may have one, that members have all contributed funds to purchase and then they share it out


    Steve
     
  4. MikeMaddox

    MikeMaddox 3reef Affiliate

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    Apogee makes a decently affordable unit, that's the one I own. Not a great way to compare LED lighting, but still very helpful. Now that I have one, I don't know how I reefed without it!
     
  5. gcarroll

    gcarroll Zoanthid

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    I was just asking to see how many reefers here have them and utilize them. They can be very helpful. I have owned one since 2004 and our club bought one in 2003 the month after Dr. Sanjay Joshi spoke about PAR to our club.

    Why do you say it is not a good way to compare LED lighting? I noticed that you have stated that PUR is a better way to compare LED lighting. Does LED produce more PUR than MH? Per your blog you stated this however are you comparing 20K MH or 10K MH or does the MH spectrum not amke a difference in PUR?
     
    Last edited: Jan 6, 2011
  6. MikeMaddox

    MikeMaddox 3reef Affiliate

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    The spectral output defines the PUR. PUR stands for "photosynthetically usable radiation" and the PUR requirements will vary amongst different types of photosynthetic organisms (plants, coral, what-have-you).

    Obviously we care about the PUR requirements for photosynthetic saltwater inverts, which is why PAR measurements have a major shortcoming when it comes to LED comparison.

    For example, there are lots of different MH bulb manufacturers, right? However, by definition, one 10k bulb should be identical to another 10k bulb (not exactly in the real world, but more or less). Hence, there is no need to compare said bulbs light output. However, many different manufacturers make LEDs, and to make things even more difficult, there are often several different models. Each model emits it's own spectrum with it's own output efficiency with it's own CRI, etc ad naseum. Simply taking a PAR meter and comparing these diodes may not be very helpful, because Diode X could be emitting 75% of it's light energy with a spectral peak of 550nm, and diode Y might be emitting 75% of it's energy as 450nm. A PAR meter will probably show little difference between the two diodes (depending on the meter, calibration, capability, again, etc ad naseum), but the PUR of diode Y is greater than the PUR of diode X for the animals we wish to keep, making diode X vastly superior for keeping photosynthetic inverts.

    It might seem technical, but once you understand the definitions and are presented with a spectrograph, you can make a PUR comparison easily - which is why I always say to not purchase an LED product that you can't obtain the spectrograph for.

    For example, Cree X series diodes offer excellent PAR, but virtually half of their output is wasted in wavelengths not useable by coral. High PAR, so-so PUR for our uses. Does that helps make things clearer? In Cree's credit, their diodes aren't made for our uses! ;)

    Other factors come into play as well when comparing LED fixtures: lumen/watt ratio (measure of light/electrical consumption efficiency), how well the diode is cooled, the quality of the internal electronics, what kind of drivers are used, etc.

    IMO LED tech is definitely the way of the future, but also IMO it's not quite where I want it to be as of yet, for our hobby's purposes.
     
    Last edited: Jan 8, 2011
  7. gcarroll

    gcarroll Zoanthid

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    Thank you so much for your helpfulness.

    Since I seem to have your attention, I have a few more questions.

    What is the PUR spectrum of photosynthetic inverts?

    You mention that " Cree X series diodes offer excellent PAR, but virtually half of their output is wasted in wavelengths not useable by coral." Are you referring to the white CREE diodes or all Cree series X diodes including the XP-E Royal Blue and Blue used in the Aqua Illumination Sol Super Blue LED fixture?

    Here is the spectrograph they provide on their website for the Sol White and Sol Super Blue.
    [​IMG]

    Or take Orphek's spectrograph? It to is weighted toward the blue light which should make it more PUR friendly?
    [​IMG]

    The way I'm seeing it both the Orphek and the Aqua Illuminations are ready for prime time. I give a slight edge to the Aqua Illuminations Sol Blue for me simply because they are heavier on the blue. We SPS keepers have long been fans of the Radium 20K and other 20K bulbs for both growth and coloration.
     
    Last edited: Jan 11, 2011
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  9. gcarroll

    gcarroll Zoanthid

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    I have edited the title hoping to get some more discussion going on this topic!
     
  10. OrphekUSA

    OrphekUSA 3reef Sponsor

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    [outdated, see my 2nd post below]
     
  11. gcarroll

    gcarroll Zoanthid

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    Great to know OrphekUSA! Do you know the luminous efficiency of your fixture. I would love to see the entire fixture on on a spectrometer like the Aqua Illumination. I think that it is a great way to compare fixtures being able to see the full spectrum as compared to the luminous efficiency.
     
  12. OrphekUSA

    OrphekUSA 3reef Sponsor

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    All specs, including luminous efficiency and the spectrograph of the full light is listed on our website. And yes, our fixture is more efficient than are AI's, in both luminous efficiency and PUR:wattage. :)

    Notice the large spike in the 500-600nm spectrum of the Sol white - this is a large amounted of useless light being emitted that does nothing but provide energy for nuisance algae, and not your coral. This is an issue that plagues all Cree-based LED fixtures!

    The Sol super blue spectral output is better than their white, with less wasted energy, but it's a blue diode, not a white (ie. a CRI of essentially zero), and even the blue diode has a crest in the ~550nm (green) range! This is due to the fact that Cree simply doesn't make a diode for the aquarium hobby.

    Check out the spectrums for our improved generation 2 Power LED diodes:

    [​IMG]

    As you can see the spectral curves of our Power LED diode is much better suited for coral growth, and contains enough light across the spectrum for a superior CRI but no spikes in wavelengths that are useless to coral.