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post #16 of (permalink) Old 08-14-2011, 12:47 AM
Wannabe Guru
Join Date: Aug 2010
Location: Wake Forest NC
Posts: 1,121
There are some times that lower PAR can appear "brighter" to our eyes than some "higher" PAR situations, but it's never comparing apples to apples and there are always intervening variables that make a mess of trying to predict it.

My 11g and 45g are both LED lit but using very different LED combos and driven at different drive currents.

The 11g has a PAR of about 30 on the sandbed and it appears quite bright to my eyes. Yet my 45g, which also has around 30 on the sandbed, looks pitifully dim.

I'm not entirely sure of why this is. If I crank the LEDs up on the 45g such that it looks bright to my eyes, I get algae hell.

I'm not sure how "green" registers on a PAR meter, but our eyes are way more sensitive to green light than plants are, so a green light that's ludicrously bright to us may not be all that useful to a plant. You'd think that this means "lower PAR" on lights high in the green area, but this is just a guess.
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