IES LM-75-19:2019 Edition

This document provides definitions of spherical coordinate systems and goniophotometer types used to measure light sources. It does not address the use of goniophotometers to measure media or surfaces. The operating principles behind each type of goniophotometer are addressed, and a general guide to goniophotometer calibration, stray light elimination, and stray light correction is presented. A methodology for zeroing data when measuring upward light is also provided. In addition, the correspondences between relevant IES and CIE definitions are described.