(in photography or motion pictures) the main light that illuminates the subject being photographed or filmed.
Origin of key light
First recorded in 1935–40
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
television theatre photog the main stage or studio light that gives the required overall intensity of illumination
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012