The Ray Flash is a piece of plastic that fits onto a on-camera-flash to provide the effect of a ring flash. Ring flashes are essential for certain macro photography, common, for example, in medical photography. When you're in close, an ordinary on-camera flash is shadowed by the lens itself, so only a portion of the subject is illuminated. As well, the ring flash is soft, because the light comes from a large area, compared to the relative point-source of an ordinary flash. Not as soft as a softbox or umbrella, but better than on-camera flash. So it combines the full-on lighting of on-camera flash, without the harsh shadows, and retains some texture thanks to the softer light source.
Click on the photos for a large version.
The trunk of my car, including the white Ray Flash box and the brown shipping box. ISO 400, 1/200 @ F/8.0, 24mm on EF 24-70, Canon 5D mark II.
Those military families are trying to invade my bookshelf. Notice how the soldiers are essentially shadowless, yet the detail is crisply delineated. ISO 400, 1/60 @ f/4.0, 66mm on EF 24-70, Canon 5D mark II.
Coffee table with glass top, antique box, glass bowl of eggs. Note donut shaped specular reflections. Notice the greenish egg on the right has a bright round highlight from the flash, and a paler, larger highlight with a vertical line from the french window behind me. ISO 400, 1/60 @ f/4 70mm on EF24-70, Canon 5D mark II.