The OL Series 455-S Integrating Sphere Calibration Standard is designed for accurately calibrating microphotometers, image intensifiers, telephotometers, and imaging spectroradiometers for photometric, radiometric, and spectroradiometric response. It is a large area, uniform, diffusely radiating source with a near normal luminance that can be varied over many decades without changing the color temperature. The source module has a 150-watt tungsten quartz-halogen reflectorized lamp with a micrometer controlled aperture between the lamp and the integrating sphere. This combination provides for continuous adjustment of the sphere luminance over a range of 106. The integrating sphere is coated with a highly reflective, diffuse coating and produces a near perfect luminance source.