Alistair
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If you have two lighting setups, one using a 400 watt HID that emits light at about 50,000 lumens with a 3000 K rating, and the second one using fluorescent bulbs with a total output in lumens also of 50,000 with a 3000 K rating; do these two lighting setups emit light of the same quality?
I was reading the link CFL Lighting 101 http://www.marijuanapassion.com/forum/showthread.php?t=8581&highlight=compact+fluorescent
It says that for every foot of distance away from the light about half the output in lumens is lost. So, if you have 50,000 lumens coming from your lights, then at a foot away you only have 25,000 lumens. Then you take the 25,000 lumens that actually reach your plants and divide that by the number of square feet in your grow room in order to determine how many lumens per square foot. Your grow room is 12 sq. ft, so you divide 25,000 lumens by 12 sq. ft, giving 2083 lumens/sq.ft.
Ok, according to the article, the plants only see about 68% of that 2083 lumens, ultimately giving the plants only 1,416 lumens per square foot.
Does the above information seem to be correct? I've always heard it said that about 1,000 lumens is lost per foot of distance from the lights. If that is the case, then at 1 ft. from the 50,000 lumen light source there still remains 49,000 lumens reaching the plants. 49,000 lumens divided by 12 sq. ft. equals about 4,083 lumens/sq. ft. 68% of 4,083 equals about 2,776 lumens per sq. ft, which is much better than 1,416.
Does anyone understand loss of light in lumens per distance from the plants? What is the best way to calculate lumens per square foot.
The reason I ask is because I thinking of replacing my metal halide and HPS lamps with 6500k fluoros for vegging, and perhaps about 3000 K for flowering. I'm thinking of doing this because the fluoros can be placed a lot closer to the plants than the HIDs. I normally keep my HIDs at about 15"-16".
I was reading the link CFL Lighting 101 http://www.marijuanapassion.com/forum/showthread.php?t=8581&highlight=compact+fluorescent
It says that for every foot of distance away from the light about half the output in lumens is lost. So, if you have 50,000 lumens coming from your lights, then at a foot away you only have 25,000 lumens. Then you take the 25,000 lumens that actually reach your plants and divide that by the number of square feet in your grow room in order to determine how many lumens per square foot. Your grow room is 12 sq. ft, so you divide 25,000 lumens by 12 sq. ft, giving 2083 lumens/sq.ft.
Ok, according to the article, the plants only see about 68% of that 2083 lumens, ultimately giving the plants only 1,416 lumens per square foot.
Does the above information seem to be correct? I've always heard it said that about 1,000 lumens is lost per foot of distance from the lights. If that is the case, then at 1 ft. from the 50,000 lumen light source there still remains 49,000 lumens reaching the plants. 49,000 lumens divided by 12 sq. ft. equals about 4,083 lumens/sq. ft. 68% of 4,083 equals about 2,776 lumens per sq. ft, which is much better than 1,416.
Does anyone understand loss of light in lumens per distance from the plants? What is the best way to calculate lumens per square foot.
The reason I ask is because I thinking of replacing my metal halide and HPS lamps with 6500k fluoros for vegging, and perhaps about 3000 K for flowering. I'm thinking of doing this because the fluoros can be placed a lot closer to the plants than the HIDs. I normally keep my HIDs at about 15"-16".
