Quote:
Originally posted by Agent86
It gives readings in foot candles not lumens so I did the conversion to lumens for the figures below. 1 foot candle = 10.7 lumen.
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Where did you get you conversion numbers from.. becuase in my book it's 1 foot candle = 12.6 lumens.. it comes from the area of a sphere with a radius of 1 foot.
so you would have to increase all your numbers by 1.2. Doesnt sound like much but here are a couple of adjustments.
1 light 1 foot
you said
3210 i say 3852
2 lights 1 foot
you said
9360 i say 11232
last 400 watt hps
you said
24075 i say 28890 ( a little closer to the bulbs rating of 36000)
But I digress.. first "why people think foot candles and lumens are the same". A foot candle is the light measured 1 foot away from a candle. A lumen is that same light over a square foot. If you measured when a foot candle/ lumen meter 1 foot away both would read the same.. but a foot candle encompasses the entire sphere around a candle to which there are 12.6 square feet or 12.6 lumens all around the candle.
ok but why argue about lumens in the first place..lumens where made up for photography.. it based on the human eye which my plants have none. For example a halogen has alot of lumens but cant grow a plant for S***. Lumens are only helpfull when comparing the same type of bulb like a 400 watt hps vs 1000 watt hps. What we need to be arguing is PAR or Photosynthetically Active Radiation or lumens for plant eyes... Par takes into account cri and kelvin temp etc. Accually there is a variation on PAR that I think is even better but I'l leave it here.
Some par watts of common lights
PAR watts of midday in the troppics.. is 2000 PAR
400 MH (110 PAR)
400 HPS (140 PAR)
1000 HM (470 PAR)
1000 hps (600 PAR)
update of interest.
lumens include green light.. which the plants dont use at all. Whats nice about this.. need to light your grow room at night.. you can safely do it with green lights without affecting flowering.