Optronic Laboratories Inc. is offering the OL series 466 automated, variable low-light-level integrating sphere calibration standard. The company says that it performs accurate calibrations of sensitive instruments under moderate to very low light levels. The large-area, uniform, diffusely radiating source has a near-normal luminance that can be varied over several decades without changing the color temperature. It comprises an optics head that is available in 4-, 6-, 8-, 12- and 18-in. diameters, and a microprocessor-controlled power supply. Calibration options include luminance, color temperature and spectral radiance.