Best way to figure light footprint??

What’s the beat way without a par meter to calculate your light footprint? I run 600watt mh/hps so I know it’s at max 4x4 feet. I’m setting up a large room but not filling it with lights. How can I correctly measure out the light footprints for 4x4 feet?? Line up the lights on the floor on like a towel and measure out 4ft per side? Easier to do while hanging?

You will probably find, using a light meter, that the footprint isn't actually a square at 4x4, but more of a rectangle. Perhaps 5x3 using horizontal lamps in a barn reflector. The reason being, that if you look at the end of the lamp, you can only see a tiny bit of that light emitting tube. If you look from the other end, your actually in a shadow. As you turn the lamp around, you get to see more and more of the tube. With maximum exposure when looking from the side. This translates exactly to the radiation pattern. A vertical lamp puts out a field that looks a lot like a ring doughnut, with the lamp dead center.

Best bet, expect some elongation of the footprint. 4x3. Or better still, get a $10 light meter. It might not measure in plant specific units, but it will accurately measure dispersion of whatever is present.

Edit: Youtube have shade comparison tests, done by a few shops. You might find your shades, or get a better feel of what go on.



How to hang them is another issue entirely. Individually isn't generally good. It's too many adjustments. You may instead put 3 or 4 in a row along a rod, and then hang the rod with two adjustable strings. So it's easy to move a few at a time, from the edge of the room. Less strings, means less effort if you want to use eye bolts as pulleys to have the string anchor points all together on the wall somewhere. pretend you had 16 lights, that is 32 strings hung as individual luminaires. Group them 4 lights to a beam, and you have 8 strings.

With any such pulley system, you add a second string from the beam the hook. This string is just loose, and serves no purpose, until the main string snaps. It shouldn't happen.. but knots can slip, strings slice on screw flanks, or the manufacturer can simply get it wrong. It's always nice to know that if you let go of the string when adjusting the height, it won't all fall to the floor.

Think about the lights, while starting your build with the carbon. It wants hanging well, and not in the way of the lights. Then put the lights up. While the room is clear to lay the stuff out.

I don't like fixing to ceilings. If you need a beam across the room, it's easy enough to put a shelf bracket on apposing walls to hold one. This is especially useful with fans&filters that shake the shit out of ceilings, but don't shake a decent wall so easily.

Do you know how to hang all that stuff in one go? Carbon, fan, mufflers.. put it all together on the floor. Lay a 2x2 along the top of it all. Bind it all to the 2x2, then hoist the lot up with two ropes. Leave it 3" short of it's final resting height and tie it off. Then, using thin bungie cord, go round the 2x2 and upper fastening point. As if adding to your rope. Slightly stretch the cord as you go round. Once..twice...3 times... at some point, the accumulation of cord, working together, will take over from the rope and become whats holding the beam up. With your rope as the 'catch'. You want to wind enough cord around to have the beam held in suspension, while the cord is in partial extension. This is important. It must be in partial extension. That is why we used a few turns of cord, to get the amount of elastic just right. This beam suspended properly will bounce when prodded with a finger. Up or down. It's very free to move. Only then will the cords transmit almost no vibration. Thicker cord that's not in extension, is still a stiff rod. Thinner cord at it's limit is no better. The mount has to be in partial extension. With a catch line.

I have pictures... ?




To round up, place shades side by side along a beam, on centers about 3 foot apart. Expecting each to light 18" to each side. But about 24" back n forth. That's your 3x4. Then have the next beam 4 foot away.