Inexpensive stretcher bars can be found in almost any art supply store. The same store should have a sheet of vellum in the same size as the assembled frame.
A fabric diffuser on a stand. Courtesy of PhotoFlex.
Lastolite makes a collapsible Ezybox softbox that's easy to store when not in use. Courtesy of Bogen Photo Corp.
RedWing's Cocoon lets you photograph small objects in diffuse light. Courtesy of Calumet.
A small diffuser can be attached to an external flash to soften the light.
A translucent plastic gallon milk bottle makes a fine diffuser when photographing small objects. Just cut out the top end for the camera lens and the bottom for the subject.
In our digital desktop studio, the lights have small bare bulbs close to the setup, so unless the subject is very small, the light is hard. To soften the light, we place a diffuser between the light and the subject. The hard light from the lamp hits the diffuser and some light passes through making the diffuser the light source. Since it's larger than the light, and closer to the subject, it casts softer light that envelops the subject and fills shadows. Some companies sell diffusers for flash units that are the same size as the flash head but have a translucent surface. The impression some people have is that the translucent material through which the light passes softens it. This isn't true. It's only size that counts. A diffuser larger than the light source will soften the light. One the same size will only dim it.
A very low-budget diffuser can be assembled from stretcher bars used to stretch canvas for paintings, and a sheet of vellum— both available from an art supply store. Stretcher bars are ideal to use for a diffuser because you buy pairs to assemble into any size frame and then tape vellum to them. These may seem simple, but even the pros use them.
The frame stretchers snap together without the need for any tools and you can attach the vellum to the frame with tape.
If you have more money to spend, the next step up the scale is a fabric diffuser, perhaps with a stand to hold it in place. If you are using strobes, the ultimate diffuser is the softbox. Softboxes are lined with reflective material and one side is a translucent white fabric. When a bare bulb fires inside the box, it's light bounces around inside the box and exits out through the translucent fabric, making the large fabric a much softer light source.
A large softbox illuminates with very soft
light. Courtesy of Smith-Victor.
The photo of the head on the left was taken without a diffuser, the one on the right with one.