I'm in a real pinch here, and I've thought up a potential solution....but it might be borderline ridiculous. lol

Basically I need a giant soft light that's suspended in the air so that it points directly downwards. It's going to hang on cables, and needs to be light weight. It also needs to be a good 4'x8' in size and must produce at least 2000w. I cant afford to rent a whack of 4bank kinos, so I've thought up the following solution.

Take a 4'x8' sheet of lightweight plywood and cover one side in tinfoil. Then mount a grid of light sockets (maybe 4 rows of 6, each at 100w). Then I'd use a sheer white bed sheet thats hung loosely to diffuse the light. hang it on the wires and point it downward. Presto.

Is this insanity, or will it actually work? lol

Make sure that sheet doesn't catch fire! I was going to suggest a Chinese lantern type of setup (hey, it's cheap), but if you need directionality I think your plan might actually work.

board would present at least 2 problems:
even balancing, and manageability.

It would be unwieldy, at best, and may end up "pointing" in one direction. Keeping it level may be difficult (if that's important to you).

I'm trying to picture how you would hang it, even with cables.

I'd consier multiple smaller units rather than 1 large one.

good luck.

True it will be unwieldy, but if you attach cables to the four corners and bring them to a center point, then attach that to your main cable, you could keep it more stable than with just one cable.

Thanks a lot guys. I appreciate the quick responses.

And on a side note, the location offers and easy way to suspend the rig...both secure and level. Thankfully, that aspect isn't an issue. :)

Better Idea:

If your budget is ever shrinking, go pick up 4 500w work lights. Place them approamately 8 feet behind a semi-opaque white shower curtain hung up between 2 stands.

Instant wall of soft light for less than $100.

(and you wont burn down your location)

Thanks for the suggestion Hunter, but there are 2 problems with that idea.

1) If the lights were 8 feet above the diffusion, the diffusion would have to be *massive*, otherwise the light would spill around it. Also, I dont have any means of getting that high up to install the work lights. My rig already needs to be pretty high up in the air.

2) I can build this rig for $50. A 4x8' sheet of OSB board is only $6, the sockets are $1 a piece, and bulbs are a dime a dozen. I need the odd extra part, like wire and such, but in total, it comes to around $50.

What about those screw in flo-bulbs? The energy saver ones.

That would kill the heat problem...but would it cause problems with the color temperature of my fill lights (which are tungsten).

Make sure that sheet doesn't catch fire!

I'd be just as worried about the wood covered in tinfoil - you're producing a huge amount of heat with nowhere to go.

I would think about vents of some sort, small holes in the foil won't matter and a vent or even a ceiling fan behind them is going to dissipate some of that heat. If the whole thing goes up in flames and covers the item you're filming - you could end up with some interesting footage!

Since you're wiring the plywood anyway, 4 fans will get rid of a lot of heat (I'm not sure if the noise would be a problem)

"That would kill the heat problem...but would it cause problems with the color temperature of my fill lights (which are tungsten)."

Nope. Most compact fluorescents are "warm white" which means they are balanced the same as tungsten consumer lamps. You may even find the 2700Kelvin rating printed on them. If you are using studio tungstens (3200Kelving), you may want to use the "bright white" nvision compact fluorescents from Home Depot that are rated at 3500Kelvin. Since you are using so many bulbs, you can even mix them to change your color temperature.

Back when I did a lot of product photography, I made a 4 X 8 foot frame of 1 X 2's, suspended over my product table. I stapled diffusion gel to the frame, something like Lee 250 or 251. I then had two Lowel DP 1K lights hung over that, flooded; and it was perfect.

It sounds like you're needing a soft, diffuse overhead light - in a 'lmited' area at low cost, right?

What you are basically suggesting is an overhead 'silk' that is blasted with the light source. As others have suggested, you can frame a 4x8 out of lightweight materials such as 1x2's or PVC pipe - and stretch your 'silk' across it. Then you may choose whatever light source you want, and place them above it. The problem with large silks and reflector boards is that they can be unwieldy and difficult to manage. They blow around outdoors, they require rigging that might be exposed in the shot, ,limiting your shooting options.

Alternately, you can use numberous china balls or 'soft cans' - that are hung from the ceiling. This is how larger sets are illuminated for soft overhead lighting. China balls are cheap, easy to hang, and can be moved around on a set.

While the color temperature rating of fluorescents may be given as "3200" etc., these lights produce a lot of discontinuous spectrum that is not accurately captured by the color temp. rating. There is another rating "CRI" which is a percentage of how well the color temperature rating is accurate. This can vary from 52 to 80 or so while tungsten for the same color temp is 99% accurate.

well that piece of plywood will sag without some 1X3's running the long way. the device you are talking about is called a chicken coop. they used to build these things was 4X8 X4 tall boxes and hang them in the studio ceilings much like giant china balls. all I can say is dangerous due to the heat. heavy, and suck up a lot of power. there's a reason these rigs aren't use anymore and it involved flames.

why not instead use 48" flo bulbs & fixtures ? much lower power draw, much lower heat.

also get some black fabric, ideally a felt like material from the local fabric store and use that as a skirt to control spill. ideally get real duvatyne.

personally I'd rent a 6X6 or 8X8 with silk, some extra tube and make a t bracket to run about 18-24" above the frame, then rig some 500W DP lights flooded. I've done some rigs like this with 12X12 in a studio and they work great. would be much safer then what you are proposing.

safety first, then cost especially when you are flying rigs like this.

Something like this might work well:

http://www.bhphotovideo.com/c/product/393718-REG/Kino_Flo_488_K32_True_Match_Lamp_.html

Are you lighting an automobile? I'm curious to know why you need an 8' softlight suspended in the air? There may be other ways of going about it.

I built and suspended the rig today. It works quite well and I managed to keep the heat levels down by adding some strategically placed vents.

I ended up using 18 100w bulbs. The whole rig cost me $60. It's now quite as bright as I had hoped, but it will suffice. I have a few ideas to brighten it up tomorrow.

All in all it was a success and I want to thank you all for your input.

And in response to Hunter, it's a set that features a pool table. I needed an inexpensive (and massive) softbox over the table to produce nice reflections in the balls.

I see, you want to create a pleasing specular highlight on your pool balls.

You can always move a smaller light source with diffusion closer to the table, but I guess you are trying to stay wide?

Anyways, here is a very cool article on maintaining proper specular highlights on shinny objects. It might be helpful for photography of pool balls too!:
http://photo.net/bboard/q-and-a-fetch-msg?msg_id=007tNJ

Exactly.

And thanks for the link Hunter...but it doesn't seem to work.

"Couldn't find message 007tN. It was probably deleted by the forum maintainer."

Either way, the shoot starts tomorrow, which unfortunately means that I don't have any more time to invest in this lighting rig. Thanks though, I appreciate the all the help I can get. :)

Oops! Fixed the link.