There are basically three things that can be done with light in a studio: it can be diffused so that it is softer and broader, concentrated to intensify and sharpen it, and reflected off many different kinds of surface. Of the three, diffusion is probably the most important treatment, as the light begins small and intense with the sources. All of the fittings shown here perform one basic function: they increase the size of the light, so that in use, the source is effectively larger. The most common materials for doing this are translucent – opal Perspex, white fabric (cotton, sailcloth or muslin, for example), gauze, frosted glass and tracing paper – while another method of diffusion is to break up the light through an open screen, such as honeycomb or cookie.

The quality of light from each of these fittings is slightly different, and the choice is largely a matter of taste. Generally, the more opaque the diffusing material, the more even the area of light, and the softer the shadows: opal Perspex, for instance, gives more diffusion than gauze. Some fittings, such as the boxed-in area lights, give greater control be preventing light from spilling out at the sides – they are more directional than, say, a translucent umbrella. The shape and appearance of the diffused light itself becomes important when shiny substances are being photographed, as they will be reflected – in this case, clean and simple shapes are usually preferred (see list below).

With electronic flash there are no restrictions on the choice of fitting but tungsten sources, particularly high-intensity lamps, must be used with caution. They are not suitable for enclosed fittings and in proximity to flammable materials. They should not be used, for instance with Perspex-fronted area lights.

In addition to softening shadows, a diffusing attachement for a studio light also has an important use with reflective objects. Under an undiffused lamp, the faces of these gold coins would be virtually illegible, but positioning an area light close and overhead give a gentle, even reflection.

Shapes that are often used include:

Yashmak – Like its namesake, a fine veil for local diffusion and light reduction

Collapsible area light – Also called a softbox or softlight by some manufacturers, this is ideal for temporary studios.

Cookie – Short for cucaloris, this open screen breaks up light into a dappled effect, rather as would leaves and branches on a sunny day outdoors.

Trace frame – Well suited to DIY construction, a grace frame is typically about the size of a door, and can be made from wooden slats.