understanding LEDs - Tropical Fish Keeping - Aquarium fish care and resources
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post #1 of 5 Old 02-10-2014, 10:25 AM Thread Starter
understanding LEDs

i'm curious about LED lighting

i'm familiar with Fluorescent lights

i'm familiar with the basic technology, i'm familiar with the lighting number (eg. 6500K) i'm familiar with how this number can be used to sell lights with completely BS expectations, ... also familiar with the expectation any reputable producer will provide with a 6500K spectrum (for growing plants)

i'm familiar with how Fluorescent lights are also typically rated with a lumen rating (it's apparent brightness as it relates to the sensitivity of the human eye (also why these lights like to have a significant green spike to appear brighter, and as such provide a higher lumen rating (that may take away from what the plants want) ... anyway, not the point of this thread


now when it comes to LEDs
they rate by PAR

i'm familiar with a color spectrum that looks like an M (in vague terms) that plants want for PUR

i see PAR as a single number (similar to the Kelvin rating for fluorescent lights)
and the skeptical part of my mind says a single number to reference a wide range of spectrum features is ripe for marketing & sales abuse

today, looking up lighting again (there's actually a lot to learn once you start)
and LEDs list a PAR rating of 30 or 48, ... and kelvin ratings of 3000, & 4000 (i guess for us old school folks)

now to me that 3-4000 kelvin rating is more red, less blue (or any combination there of) then what would keep plants totally happy

so what is a good PAR for plants that delivers a nice light spectrum for plants ?

why is any particular PAR rating good over another PAR number ?

i'll continue looking into this, but as last i looked about a year ago, i gave up after lots of disappointment at a lack of information.

so now i'm asking here hoping to find some answers i could not find before
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post #2 of 5 Old 02-10-2014, 11:19 AM
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It depends on what you are keeping so I go with a dimmable unit that has two channels this way I can change the PAR and the Kelvin rating,once you have those things you want higher PAR seeing you can simply take it down a notch if need be or simply raise it up and utilize it for a larger foot print.Most people aim for a 30-40 PAR on the substrate for moderate lighting plants further up the tank this will drastically increase.

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post #3 of 5 Old 02-10-2014, 11:39 AM Thread Starter
but what does 30-40 PAR mean on the lighting spectrum ?
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post #4 of 5 Old 02-10-2014, 07:38 PM
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You can achieve those PAR numbers under varying degrees of spectrum such as 5,000 Kelvin or 20,000 Kelvin.

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post #5 of 5 Old 02-11-2014, 08:25 AM Thread Starter
i'm lazy at the moment (so no pictures to prove what i'm saying)

fluorescent lighting spectrum seems to be rather subtle with spikes where key interest in plant photosynthesis take place

the bits i'm seeing for LED (now vs. what i saw a year ago - technology sure has improved in such a short time) LED seems to be a much more even curve that tries to reach a full curve, ... sure some spikes at key points, but over-all it looks like it closer matches natural use by the plants.

maybe i'm out to lunch, maybe i'm making assumptions, maybe i'm going by initial pictures only.

but looks promising so far, ... going to keep looking.
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