photometric units

Photometric units measure the brightness of light as perceived by the human eye. Key units include lumens, which quantify the total amount of visible light emitted by a source, and lux, which measure how much light illuminates a surface at a specific area. For example, a flashlight's lumen rating indicates how bright it is overall, while lux tells you how well a surface is lit in a particular spot. These units help us understand and compare how bright different light sources appear and perform in various settings.