Aluminum Foil Lighting

Could one use Aluminum Foil on, say, cardboard to make a light deflector for filming outside?

Yes you can! Corridor Digital on Youtube even mentions it in this video here. I don't really know how you'd go about doing this, however, there is probably some tutorials on Youtube if you searched for them.

A big piece of white foamcore is used very commonly as a reflector. Its cheap, light, easy to handle, and gives a generally softer, more pleasing light than foil. If you need a harder light, then the foil can be a good option, but a lot of people use foamcore.

Yeah, just tape foil to cardboard, that's what I did and it works really well

A more durable substitute for foil would be to use a screen for a car windscreen- you can usually pick them up from poundshops- they're designed for the interior of your car to reflect some of the sun away from your car so would be perfect to reflect light onto your actors! Like i said- you can pick them up in pound shops and the like but a quick search of google has something similiar :

http://www.autobrite...-protector.html

They're usually as reflective as foil but a lot more durable than tin foil- it's less likely to tear- would have less creases and you could probably iron it to keep the surface smooth!

I read somewhere that to get a caustic lighting effect like light shining off of water that some productions uses a small tray of water with a light shining on it with a sheet of crinkled aluminum foil in the bottom. a couple grips would move the foil around to create the caustic bouncing light on the scene. Not actually tried this myself, just read it had been done that way

A big piece of white foamcore is used very commonly as a reflector. Its cheap, light, easy to handle, and gives a generally softer, more pleasing light than foil. If you need a harder light, then the foil can be a good option, but a lot of people use foamcore.

If you use Foam Core does the surface need to be shiny or have a matte look to it. I'm Assuming this is the board you find in the art section of stores? Thanks!