SSI Standards

SSI measures the similarity of a spectral power distribution (SPD) of a test light source to a specified reference. SSI was designed to serve as a tool to quantify the predictability of light sources when used for cinematography. Unlike indices that seek to quantify a source's effect on color rendering, such as CRI and TM-30, SSI's calculation is independent of any spectral sensitivity (such as that of human vision, a particular digital camera, or photographic film). SSI has been adopted by manufacturers of cinema lighting equipment and color measurement tools to provide a reliable indication of how closely surfaces lit by a given test source will compare to the same surfaces lit by a known reference source when photographed. SSI is managed by Technology Committee 10E [link]