Heh I give no credibility to that thread simply because thats 200w of CFL light and 250w of HPS.
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50 watts wouldn't make much of a difference if CFL's weren't so bad at what they do.
First off you cant make an even comparison between the two because a 6500k CFL is a vegging light and a 250w HPS is a flowering light.
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Yeah, but I am in veg, not flower. This should give the cfl an advantage, or at least make up for the 50 watts difference, but the flowering hps light is WHOOPING the 6500k veg light of the cfl's. The CFL's should at least make up the difference because it is giving off all 6500k light, but this is not even close to what's happening. The HPS is absolutely KILLING the cfL's.
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Put simply, Plants grow differently in different light spectrums. Red spectrum will make the plants grow far faster but they are lacking the daylight (6500k) they need in veg.
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If they are growing faster in Veg with the hps, then how are they lacking?
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Secondly 200w and 250w is a fairly large difference aside from the fact HPS puts off more raw lumens than CFL.
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That's right, and the fact that the cfl is putting out all 6500k light, supposedly just what the doctor ordered for veg, should even things out, but the hps is growing ten times faster, IN VEG!!
avg lumen per watt
HPS: 130-140lm/w
CFL: 70-90
Now when I say raw lumens I mean overall spectrum. HPS light produces much of its spectrum in an area of the PAR (Photosynthetically Active Radiation) that is far less active than the 2700k and 6500k CFLs.
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Right, so the CFL, putting out 200 watts in 6500k should easily stay up with the hps putting out what is basically the WRONG spectrum, but this is not holding up in my grow. The HPS is shockingly better IN VEG
And btw 2700k CFLs put off more lumens than 6500k
In short CFL's produce less light in a more active area of the par spectrum.
Also when considering lighting and lumens you have to remember the "inverse square law" this scenario isnt subject to it but most HPS systems are.
To quote my lighting article
"To Create a Star" , "
Lumens divided by (distance squared in feet) equals lumens per square foot putting distance into account."