An adjustable lens with a self-illuminating scale for use in photography, cinematography, or videography has a housing surface with scale markings and an opaque member with a reference marking mounted over and movable relative to the surface. The movement of the member normally adjusts a parameter of the lens. The scale markings are visible through a window in the member. The edge of the member adjacent the scale has an opening. A light source is situated within a recess in the member adjacent the opening. Light is directed from the light source through the edge opening in a direction along the surface of the surface such that the visible scale markings are illuminated, while light from the light source is otherwise substantially prevented from escaping from the lens. The activation and intensity of the light source is controlled by movement of the member or an external illumination controller.