there few little bits of wrong info in that Andrew. first they say secondary optics are expensive costing between 25 to 50% of the LED.
a cree led is a shade over 6 bucks and the optic is 1 buck.. not realy expensive at all. as for spotting this is easily overcome with spacing. make you max spacing between LEDs 2" and between rows 3" and you can run 40 degree optics. I am spacing mine at 1.75" and 2.5" respectivly.
I don't know why anyone would want to run 8 degree optics but I am assuming that was just and example. 40degree optics will give you about 250 MH levels or bettwe, 60 degree will give you 150 watt mh or better and no optics will be like running T5's . now of course this all depends on the distance. on a shallow tank you might be able to use 60 degree optics and get the same PAR as a 250watt MH.
the down side to optics is simple.. the lower the degree the tighter the spacing of the LEDs must be to avoid spotting. so if you want to run the 40 degree optics you must use more LEDs to cover the same space. a good example is the system I am building. with no optics I can get away with 16 leds to evenly light a 30 gal tank. If I wanted to run 60 degree optics I would need 20 to 24 LEDs but I want lots of par so I am going with 40 degree optics so I need between 36 and 48 Leds (depending on how I arange them. so in a way optics are more expensive but not much and the extra expence isn't because of the price of optics but rather from the extra LED's needed.
Now having said this, I will probably hit 250 watt levels in my ank with no optics (tank is only 17" deep) but I want to be able to go even higher than 250 watt levels to test a couple theories
If you want to see some good info on LEDs I am going to recomend a left field place. RC has a couple good threads, but overall not much else. Nano_reef.com is the most info and support I have ever seen for LEDs. they have one guy there "the LED god" who designs lighting systems and is actualy very helpfull with questions about LED lighting. I usaly don't recomend boards other than Canreef as I generaly feel we have all the info some one needs unless they want to get way over the top, but this is one time I will say that the nano board is the board for LED questions and info.
Steve
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