An iris diaphragm is a type of continuously adjustable lens aperture made from overlapping metal leaves. By changing the size of the opening, photographers can control the amount of light entering the camera, which directly affects exposure, depth of field, and image sharpness.
Understanding the iris diaphragm is essential for photographers seeking precise control over their images. Adjusting the aperture allows for creative effects such as blurred backgrounds or starburst highlights, as well as technical benefits like maintaining proper exposure and optimising sharpness across the frame.