1. an instrument that measures the intensity or brightness of light
Usage: technical; used in physics, astronomy, and photography

Examples

• The photographer used a photometer to determine the correct exposure settings for the shot.
• Astronomers rely on photometers to measure the brightness of distant stars.
• A photometer can detect even very faint light sources in laboratory experiments.
• The digital photometer displayed the light intensity in lux units.
• Before filming, the cinematographer checked the lighting with a photometer.