The diffuser is used to create exposures of even density over the entire surface of film. Use the diffuser by placing it flush against the front of the lens and exposing through it. The light that passes through the diffuser and on to the film will create an even density across the surface of the film. Flash straight on if without our diffuser causes the light to go forward only and creates a harsh shadow behind the subject. The flash with our diffuser installed and tilted at 45 degrees gives a nice soft wrap around of light with a soft shadow behind the subject.