Stainless-steel iris diaphragms from Knight Optical (Harrietsham, Kent, England) enable smooth, continuous aperture control in imaging and microscopy applications. The components control the passage of light in optical systems; as the blades slide sideways across each other, the aperture can open or close to allow more or less light to pass through. The diaphragms are protected from corrosion in normal atmospheric conditions and offer enhanced temperature resistance in high-intensity applications up to 400°C. Versions with with blackened sprung-steel leaves that reduce reflection are also available.