Shutters are used to control the level of light exposure to an optical lens or lens system in a range of applications such as imaging or microscopy. Shutters are manually or motor controlled irises that may be opened or closed to control the level of light that passes through the aperture. Shutters provide an accurate, stable level of light transmission that may be easily adjusted or maintained for repeated implementation. A number of motorized shutters are also available that include several iris control modes for increased versatility.