The beauty dish is essentially a method of creating a soft light. However, the high sides and parabolic shape creates quite a focussed beam. The beauty dish works using two reflectors. The first is immediately in front of the light source. This little reflector is placed in front of the light so it can reflect all the light out to the sides of the main dish. The reflected light hitting the sides of the main dish is then reflected out directly at the subject. Most of the light is directed forward because of the high sides of the dish.
As the beauty dish is a big reflector bowl it tends to create a soft light. The effect of a beauty dish is to produce a softer light than a directed beam of light from a off-camera flash or studio strobe unit. However, despite being a wide reflector it creates creates a harder light than a softbox.
The effect of the light from a beauty dish is is to create a contrasty light. It is useful in developing a dramatic effect. The soft, focussed nature of this type of light creates a great wrap, with lovely soft shadow graduations – particularly flattering on the face. Being round, and quite focussed, it also creates well defined catchlights in the eyes. These are very important properties for fashion photography.
Beauty dishes come in a huge variety of sizes. The bigger the dish, the softer the light it produces. The smallest, used for off-camera flash units, may only be 150 to 200mm across. Large ones may be as much as 2meters or more across. The different sizes of the dish give relatively softer light (wide dish) or harder light (small dish). Big studios may have a whole range of sizes to suite different lighting requirements.
For more views of beauty dishes and the sort of pictures they take see:
Google images search for “Beauty Dish” .