A luminance meter is a device used to measure the brightness of light emitted from a surface. It quantifies the amount of light that is visible to the human eye, typically expressed in units called candelas per square meter (cd/m²). This tool is essential in various fields, including photography, cinematography, and lighting design, to ensure proper lighting conditions. These meters work by using a sensor that captures light and converts it into an electrical signal, which is then displayed as a numerical value. Accurate measurements help professionals achieve desired lighting effects and maintain consistency in visual media, making the luminance meter a vital instrument in the industry.