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, film production, and architectural lighting design, ensuring that lighting conditions meet specific standards. These meters work by capturing light through a sensor and converting it into a readable value. Users can then assess whether the luminance levels are appropriate for their needs, helping to create optimal lighting environments for both aesthetic and functional purposes.