Lighting Paper Lanterns

June 13, 2007 12:42 PM

A question about lighting for my wedding. I am making lights for my wedding, which essentially will be in a tent. I am making a bunch of fixtures and each fixture will have 3 to 7 paper lanterns hanging in clusters. The problem is that the lanterns are either 12, 14 or 16 inch diameters and I want to find a way to make sure that all shine equally as bright.

Essentially I am ordering equipment to build your own christmas lights. If each 12" lantern has two 7Watt bulbs in it, how many bulbs should each 14 and 16" lantern have so they shine as bright? I don't want to vary the bulb intensity, but rather the number of bulbs in each lantern, as I think this would probably be easiest for my brain.

So, should I consider the total number of Watts per unit of volume, or per unit of surface area, or does it not really matter?

Any thoughts?

Thanks.

posted by commissioner12 to Technology (9 answers total)

My gut feeling is that the apparent brightness of the surface of the lanterns will depend on the surface area.
posted by Good Brain at 12:50 PM on June 13, 2007

My thinking is that you are measuring the amount of light that hits the paper. The only factor is the distance between the center (where the bulbs are), to the paper. If your measurements are diameters, this makes the radii (about) 6", 7", and 8". I don't think it will be noticeable between those distances. Put me in the "not really matter" camp.
posted by rakish_yet_centered at 1:15 PM on June 13, 2007

This is where mock ups are helpful. You can play with formals all day long but it is going to come down to personal perception. Start your string and make one with 3 bulbs and one with four and play with it like that.
posted by wile e at 1:19 PM on June 13, 2007

2 x 7 watt bulbs are not going to really shed any light of appreciable use. Even if these are strictly decorative, I would advise going with something brighter. Peir 1 Imports sells lanterns in kits with a standard base and cord with 2 prong plug. Get a few of those and put 6 watt bulbs in them. You'll actually get some light out of them that way. You could also buy sockets, lamp cord, and plugs at a home improvement store and wire up your own.
posted by cosmicbandito at 1:31 PM on June 13, 2007

Response by poster: I guess that's the other question. Are ten 7 Watt bulbs equivalent to a single 70 Watt Bulb when it comes to light output?
posted by commissioner12 at 1:36 PM on June 13, 2007

Light diminishes in direct proportion to the cube of distance, so small increases in distance can make for a much dimmer illumination. Testing is the way to go. For a really clean effect you might want to double up and put a smaller diffuser inside a larger one, with a brighter light.
posted by StickyCarpet at 2:57 PM on June 13, 2007

Honestly, your best bet here is to experiment, just like wile e suggests. Maths will not save you here.
posted by davejay at 2:58 PM on June 13, 2007

10 7 watt bulbs might be more or less than 1 70 watt bulb. The wattage rating is for power consumption, which may not be directly linear with light output - you want to look at the lumen rating instead.
posted by 0xFCAF at 3:07 PM on June 13, 2007

Best answer: The perceived light output declines in proportion to the square of the distance. Therefore a ratio of 36 to 49 to 68 for the 12, 14, and 16 inch lanterns. From a pair of 7 watt incandescent bulbs you should get around 156 lumens, so you need 49/36= 1.3611 * 156 lumens = 212 lumens for the 14" (a little less than 3 X 7 watt), and 68/36 = 1.888 * 156 = 295 lumens for the 16" (a little less than 4 x 7w). However, this may fall apart completely in the real world, as I expect any variation in material and placement in the tent will make a more profound difference in perceived brightness.
posted by BrotherCaine at 4:08 AM on June 14, 2007