A diffusion panel is used to diffuse or soften studio light or natural light that is falling onto your subject. Generally, diffusion panels are constructed as a metal or plastic frame covered with semi-transparent material which allows light to pass through it. The light hits the panel and becomes smooth and soft, creating a gentle light that wraps around contoured surfaces and creates a gradual fall off. Diffusion panels come in many sizes and are often used as the only light modifier between the subject and the key light.
In the studio, a strobe with barn doors can be fired into a diffusion panel to create light similar to that made with a softbox. The barn doors can be used to control the effective size of the light source.
Diffusion panels are often used outdoors in harsh sun light to create an artificial shade. The light that results from sun through a diffusion panel is very pleasing and soft. In fact, many studios use white curtains over large windows and daylight as the key light in their images.
Diffusion panels can be portable and collapsible or mounted on a panel stand. Diffusion panels can be home made as an alternative to commercial diffusion panels. A basic home built diffusion panel could be constructed from translucent white rip stop nylon mounted to a PVC tubing frame.