formula for calculating Lumans/Square foot?

Discussion in 'CFL / Fluorescent Lighting' started by Geezy101, Feb 18, 2012.

  1.  
    Geezy101

    Geezy101 Active Member

    anyone know how to find that out?

    i have 55,000 lumans for a 4x4x6 tent? how many lumans per square foot?

    Cheers
  2.  
    afrawfraw

    afrawfraw Well-Known Member

    55,000/16= 3437.5

    OR 573 Lumens per CUBIC foot.

    Basically, the floor is square feet. So I'm assuming the floor is 4X4. If not than 4X6=24

    So 55,000/24=2291.6 Lumens per square foot if it's 6 feet long. If not, go with the original.
  3.  
    Geezy101

    Geezy101 Active Member

    thanks for the response, not gonna lie that did confuse me.. reason i ask is they say 2,500 lumans per Square foot is ideal. I found a forumala after like 30 min of searching online. annnd its pretty straight forward.. lol

    LxW=?
    4x4=16

    i want at least 2500 lumans for square feet. so i then calculate

    16x2500= 40,000 lumans

    so i would wanna run lighting that offers at least 40,000 lumans for my grow space. which i do..

    sound about right partner?
  4.  
    afrawfraw

    afrawfraw Well-Known Member

    Yup, yer right at 3,437.5 Lumens per square foot. Just remember lumens fall the further away from the bulb you get, so that's 3,437.5 lumens AT THE CANOPY. If you want that all over the plant, you'll have to side light, but that's another story.
  5.  
    HydroDawg421

    HydroDawg421 Active Member

    So if I have (2) 1000w HPS + (1) 400w HPS, I have 350,000 total lumens. Divided by 16sq ft (4'x4) = 21,875 lumens per sq ft.

    That seems like a LOT!!! Is my math correct?
  6.  
    Geezy101

    Geezy101 Active Member

    ahaa i see how u calculated that now. ur way got exact what i have to offer. good stuff bro. yea i hear.. ill prolly bend my plants during flowering to help utilize the lower half. all seeds i purchase i made sure it set in the write up that the strand is okay for that technique.

    cheers partner!
  7.  
    Geezy101

    Geezy101 Active Member

    SICK fawkn setup dawg.. just have one thing to add. clearly u have balls when it comes to lumans. im no expert, but would it be better to have ur light horizontal rather than vertical? maybe in ur case since ur soo wide maybe u have the right technique.
  8.  
    afrawfraw

    afrawfraw Well-Known Member

    LUMENS DO NOT STACK! Any one who tells you this is just wrong. I would calculate the lumens from 1 bulb on top. This is the lumen level period. Now it drops as you move away from the bulb. The key is if your using more than 1 bulb, you can apply that lumen level to lower levels/wider areas. So a 600W Digi throws 95,000 L. 2 throw 95,000 L, but cover more ground, or I can drop one to the side, and maintain that 95,000 in the lower branches, so I'm not wasting nutrients on larfy (Useless) buds.

    Also realize, I can't see your 1,000, so you would need to use inverse square law to calculate the lumen level AT THE CANOPY, not the bulb. If the 1K is 2 feet away, it's applying about 8,000 lumens. Less if their is glass between the bulb and the plant. Your 400 at 6 inches casts around 6,500 lumens, but casts it's beam horizontally, to penetrate colas.
  9.  
    HydroDawg421

    HydroDawg421 Active Member

    I have (2) 1000w light hung horizontal about 36" above the canopy and (1) 400w hung vertical.
  10.  
    HydroDawg421

    HydroDawg421 Active Member


    Soooo . . . Based on my setup what's your best guess of the lumens at the canopy? My 1,000w lights are about 36" above the canopy and the 400w about 6" above the canopy.


    17409316.jpg

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