Step 3: Just Add Walls

Since you're building this box to diffuse light, use material that's heavy enough to evenly disperse your flash or whatever light source you use. Ripstop nylon is ideal; heavy cotton sheets work in a pinch; thin, sheer fabrics like silk and linen won't completely neuter the flash and will likely create a hotspot. Attach the two side panels with tape if you're in a hurry, or use Velcro tape if you think you'll ever want to change your material to a different color or weight for special lighting effects.

If you want to skip the tape, just drape a big sheet of nylon over the top and call it a day.