Light spectrum data base

Discussion in 'Planted Tank Equipment' started by Greystoke, Aug 22, 2010.

  1. Greystoke
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    Greystoke Specialist

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    I got my hands on a number of light spectra, and converted them to arrive at PAR, and Lumen values. I will carry-on with this exercise in order to get a reasonable data base, and I'm making the xls-file available to our members.
    Fluorescent light Spectra Database
    LED light Spectra Database

    If you wish, I can include your lights to the database. Just give me as many particulars you know about them.
     
  2. tyronegenade
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    Cool, thanks! I always thought the Power Glos were good value for money as far as "aquarium lights" go. Of course, it is the LEDs which are the real winners PAR/W wise. Bang for buck, daylights seems the best bet based on the available data. Now I just need to move my lazy ____ and get some attenuation data for aquariums and then we can have some idea of which lights offer the best penetration into the aquarium water.
     
  3. Greystoke
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    I'm actually getting a bit suspicious about the results that I'm getting [​IMG].
    When you look at 'Table' in the data base, you find the efficiency varying between 13.88% and 29.04%. That does not make sense !
    The efficiency depends on the technology in use, and since the technology is the same (ie: Fluorescent Light Sources) the efficiency should be the same (give or take maybe one percent variation across the range). But certainly not 15%.

    [​IMG]

    The efficiency is the ratio between the amount of power (Watt) dedicated to generate (photopically corrected) visible light, converted to Lumen (=100%), and the rated Lumen output of the light source.

    The power calculation may be one error source, as some tube generate a lot of power outside the 400 to 700nm range. The gross power consumption should therefor be derated to exclude that part.
    I've already corrected most of them, and so far it made little difference, which means that there is one final suspect: The rated Lumen output for the light source.

    I may have misinterpreted some published data, but - frankly - I suspect that the published Lumen ratings are misquoted to a degee of plus and minus 30%.


    PS: Tom Barr advised the members of his forum to buy their own PAR-meters. I can now understand why.
     
  4. wearsbunnyslippers
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    yeah, a PAR meter is the only way to go apparently.

    i saw another post where a guy bought a new bulb, same specs as the old one, but when he measured it with his PAR meter, it was 30% brighter than the first one he had when he bought it. so i dont think a chart or calculator can ever be anywhere near accurate enough, if you have to account for 30% discrepancy...
     
  5. tyronegenade
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    What if the previous "new" tube was already warm when the PAR measurement was made? This would decrease the output.

    We need to get some PAR meters and get some decent experimental data.

    Cor, I think some variation in photonic output is to be expected between the tubes. To achieve a particular spectrum different phosphor mixes are used and the energetics of each will vary. You comment about photons outside the PAR spectrum is also important to consider. While some UV is invisible to us it is important for proper biology.
     
  6. wearsbunnyslippers
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    he did mention he waited for the tubes to warm up, as someone else commented on this too. i will try find the post...
     
  7. Greystoke
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    Greystoke Specialist

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    I think so too, but no more than a few percent. Also (Wikipedia):
    I understand that this rate is common throughout the range, so the efficiency variation I'm getting, MUST BE the result of erroneous inputs.
     
  8. Greystoke
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    Idea!

    If I plot the "visible" output of the tubes, as derived from the photopically weighted spectrum, and present it as a percentage of the total power, then this MUST logically give me an indication of the lumen output per watt of the total power.

    In other words: The visible output [Watt] per Watt of input power, should be equivalent to the tube's lumen per Watt rating.
    So, If I plot the Rated Lumen per Watt of each tube against the visible output as a percentage of the total power, I should get a straight line relationship.

    Well, gues what? Here's the relationship:
    [​IMG]

    If you look-up the data base, you will find that some brands have reasonably accurate Lumen ratings, but the real culprits are the centre three in the middle of the graph. Just can't figure out why.
    The tubes are (frm left to right):
    a 58 Watt T8 77 FLUORA, a 15 Watt T8 9325k GE and a 54 Watt T5HO 18,000k Hagen PowerGlo
     
  9. Greystoke
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    Hi Guys,
    I think I have some startling news.

    In my opinion, it would appear that some tube spectra, as supplied by the manufacturer, are questionable. This is not something they (the manufacturers) have admitted, it is the conclusion one arrives at after the answers you get.

    I mean:
    If you determine the luminous (visible) output of a tube by analyzing its spectrum, and then compare it with the rated Lumen output, surely they should relate to each other.
    But what if they don’t? Well, in that case:
    1: Either the rated Lumen output is incorrect, or . . .
    2: The spectrum is incorrect, or perhaps . . . .
    3: I am incorrect.

    As for that last point, if I made a mistake, it should be a consistent mistake throughout the range, but that’s not the case. Most tubes seem OK. I just get a few odd balls. So a mistake on my side seems unlikely. Yet, you never know. I’ll keep checking.

    The Lumen rating is highly unlikely to be incorrect. It’s one of the most published parameters, which are also used by lighting experts, and if incorrect, there would be complaints very soon, and the value would be corrected quickly.

    That leaves one culprit, ie the spectrum.
    No-one uses spectra. Why should people? It’s just that WE could derive the PAR and PUR values of the tube. That’s useful information. But otherwise . . . . no-one else cares.

    A spectrum can be wrong for a variety of reasons. However, in most cases I believe they are being muddled up. I have heard of that a few times on other forums.

    I’m at a loss as to what to do about this. Perhaps we should be aware of the tubes that don’t seem to have an accurate spectrum. That doesn’t mean you can’t use the tube. If you’re happy with them, obviously use them, but remember those manufactures that supply accurate information. It’s much more to our advantage.
     
  10. wearsbunnyslippers
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    you must also remember these guys are also human...

    if they have an order of 100 000 tubes to fill and then run 20 000 short, they can just buy a similar spec from one of their competitors and rebrand it, this happens all the time with all sorts of products.

    also different manufactures around the world have different specs and tolerances so a tube mad in china might be slightly different to a tube made in india and different again to germany. then when people are importing they get from the cheapest supplier, or one company does an interbranch transfer to get stock from another country and you can end up with two different bulbs even though they seem to come from the same batch...

    i dont think this will ever be an exact science without PAR readings. and even then, if the tank owner changes bulbs, they need to do another PAR test...
     
  11. Greystoke
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    Greystoke Specialist

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    Hmmm,
    I suppose you're right, but that leaves us with an unholy mess.
     
  12. Greystoke
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    OK,

    QUESTION @WBS: How would you select new tubes for your tank aside from power?
     
  13. wearsbunnyslippers
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    color and reputation.

    the dutch guys, use phillips a lot. the uk guys like osrams.

    the tubes must end in 65 for the 6500k, and then some other colour tubes to balance the colours so it looks nice to me. sylvania grolux and arcadia plant pro also work for me. the arcadias are very over priced.

    osram lumilux 865
    phillips de lux pro 965

    you are guaranteed to grow plants with these tubes. getting the color balance right is another story.

    http://saurama.aqua-web.org/index.htm
    http://www.theplantedtank.co.uk/lighting.htm
     
  14. Greystoke
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    Color and reputation?
    Fair enough.
    Perhaps we shouldn't make such a fuss about it and concentrate more on keeping it simple.
    On the other hand, the manufacturers are tight-lipped about technical information. I tried to get it out of them how they work out the Kelvin rating from the spectrum.
    Answer:
    :
     
  15. wearsbunnyslippers
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  16. plantbrain
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    plantbrain Noob

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    In general, the questions an variables and error ranges are often quite large, it pays to use a PAR light meter, borrow, steal etc.........

    Why guess with respect to light then be all methodical and critical with nutrients, when CO2 is the thing that most kill/stress or harm their fish with?

    Aquarist should be much more focused on light and CO2.
    It makes all management questions and issues much easier to achieve a given goal.

    Regards,
    Tom Barr
     
  17. Greystoke
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    Yeah, yeah, but we're the poor clan here. I don't even know anyone who has bought, borrowed or stolen a PAR meter. [​IMG]

    Anyway, even though there is a hugh information gap, I find that if you keep pushing the manufacturers, they will eventually give you what you want to know, and some are actually quite generous about it. Most have done extensive tests with their lamps in nurseries and on aquaria. They know what they're talking about, and they have the answers.

    Our hobby is also not that critical. If you can estimate parameters to within 10% accurate (Lumen or PAR), then that's just perfect. And if a manufacturer can give a representative spectrum of his lamp, then it's possible to work out most pararmeters to within that margin of error.
     
  18. plantbrain
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    Well, ADA's tanks appeared to have a reasonable amount of light.
    But.........I actually had the gumption to measure 6 of them critically.

    They all had the same range, about 40-50 micromols along the bottom surface.
    the Watt/gal rule predicted an error of over 50%. Or 80-100micromols.

    So ADA's tanks/lights where much less efficient than anyone predicted.
    It was also interesting that each of the 6 where so similar.
    PAR meters can be purchased as a group to defray the cost, they are also very easy to use.
    So if a group of 20 people put in say 20$ each, then this is about the cost of a NO3 test kit or close. You really do not need a light meter much, a few times maybe once every 1-2 years to keep tabs.

    You can also see how little light is required by certain species and how algae responds.
    Or how cleaning the sides of the tank helps with increasing light PAR, or different brands of reflectors, or glass lid effects, or evenness of spread vs closer hot spot intensity.
    Differences in water depth and distance from the bulb etc.

    Being cheap is good, but you are clever enough to find ways around paying so much by pooling resources, then it becomes much less of a challenge to the pocket book.

    You can also buy it, then sell it back, some folks rent theirs.

    We have found far larger errors than 10% and ADA and many companies are not as forthcoming.
    Since we have to assume the ADA tanks that place in the top 25 are pretty good examples where we can safely say that there is ample sufficient lighting for most any aquascaping goal, these make good reference points.

    Here's one such tank I measured:

    [​IMG]

    By using tanks where we find no issues with algae and plant health, this allows us to falsify hypothesis we might have held onto strongly in the past. So if high light is NOT required, what is a good optimal level?

    Regards,
    Tom Barr
     
    Last edited by a moderator: Apr 11, 2014
  19. Greystoke
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    I can't fault you on your findings, and I certainly do not question your expertise and recommendation. I agree that a PAR meter is "nice to have", but I think one can do acceptably well without.
    The "Communal" PAR meter is a good idea, and we should think about it, but it presents a problem with posting around the country. APSA has members all over South Africa, mostly in Jo'burg and Cape Town, whereas I and a few others are in Port Elizabeth.
    What say you about this statement?
     
  20. plantbrain
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    Well, we aquarist have managed to do fairly well without such measurement and equipment, but a lot of trial and error. We all have done so, or/we have quit:)

    The goal here is to really look closely at the nice examples, or reference tanks..............then see what we can learn about light. There's many myths about light, but it seems central to success for many aquariums.

    By looking at light, much of the so called differences are not that different suddenly, which makes much of the speculation and unknowns go away. Now we can see why supposedly different tanks can/may behave the same with regards to lighting.

    If you compare with PAR, they are the same, if you estimate or try and compare say a tank using X brand in SA or in the US, you could be off by a factor of 2-3x using watt/gal.

    So you might have what you think are similar results, but the other guy might have 2-3x more light than you have. But that's not really the whole story or the case. This stuff can easily lead to myths and problems when help new folks replicate a good set up to get a similar goal.

    So we have much more knowledge and understanding of the variation between lighting types and each unique tank's light intensity. Can an experience aquarist do it without? Sure. Could they maximize their light usage and replicate easier with? Certainly. A few get lucky, a few get unluncky and quit the hobby if they cannot manage light well, which makes managing CO2 and the rest that much more difficult.

    A good handle on light makes helping and retaining people in the hobby that much better.
    Then we can move to CO2, Excel or no carbon enrichment methods and so on down the line.

    I have an older Apogee model I might be able to sell you folks. We might go with the newer model soon. They both work well, just the older one cost less and is a different model. Some advancement eh? Charge more and pretty much the same.


    Regards,
    Tom Barr
     

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