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. This fits cleanly over the head of your existing flash, no need for cumbersome attachments, hooks. Try us and see the difference.