New light meter, and I'm shocked! Does this sound right?

jawbrodt

Well-Known Member
I bought a digital light meter yesterday, and just checked my bloom room, and was shocked to see some of the readings. I have a 600 watt HPS, and two 400 watt HPS lights. I have one of those 4 foot wide 'sunsoaker' reflectors on my 600, and regular reflectors on my 400's. I have the 400's placed right on the outside edges of the sunsoaker, and the light opverlaps. I was getting around 3500-5000 lumens directly under the sunsoaker, which seems normal, but I was getting almost 8000 where they overlap. Holy fuck! :shock:

When I held the meter 4" away from the 600, the reading was like 12,000, and at 2" away, it broke 20,000 and was over the meters limit. :shock: Does that mean that if i had a vented hood, and ran that light 2" away, that i would be getting 20,00 lumens per square foot? I don't plan to do that, but holy fuck, I was getting alot higher readings than i thought. :shock:

Here was another shocker.....I was checking under the 400 HPS(55,000 lumens) and getting like 6,000 lumens at 8-10" away. My closest plant is like 12" away and was getting like 5,500 lumens. Holy shit, i was going to add another 400 and pack the light closer together, but I don't think it's necessary, if I'm reading that right. :shock: I'm at the point of needing CO2, I think?

Here's my main question....the meter measures in footcandles, and i thought that would be different from 'lumens per square foot', but when i looked up the conversion, it said that they were the same thing. Does that sound right? I'm 99% sure I am, because i googled it and read it on a couple different conversion sites, but i just want to hear it from somebody who checked their own system?

No wonder i had problems with 'bleaching' last time, I was probably getting over 10,000 lumens at the closest plant. I thought it was a N deficiency, but now I'm thinking it really was bleaching? Also, I didn't think that a 400 was capable of that kind of power, but i guess if you use it to cover like 6 square feet, it does? Holy shit! :shock:

Confirmation?
 
I dont think that the overlapping would hurt the plants, ive saw where some bulbs put out 50,000 lumes. Im trying to figure this out myself though. I just switched to a 600 w digi hps and need a light meter.
 

SimonD

Well-Known Member
I use a light meter. The numbers, themselves, aren't that relevant. What matters, however, are the relative readings. Meaning, one number compared to another. Good luck.

Simon
 

oldMcDonald

Well-Known Member
i use LEDs so i get 2'' or closer, but i hear if you do it with HPS even if its vented you'd still burn your crop that close. as for the overlaps...
people have this idea in their head that light hits more intensely under itself. light doesnt fall, its massless. if your 1 foot away above or below or on the side of the bulb, you're receiving the same amount of light. its just preferable so your plant will grow straight up rather than sideways. as for the foot candles and lumens per square foot conversion, i dunno. maybe a footcandle is how much light is in a square foot that is one foot away from a candle, but not 100%sure.
 
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