Which instrument is used to measure the luminance of a monitor?

• A. Photometer
• B. Lux Meter
• C. Goniometer
• D. Colorimeter

Answer: (A)

Luminance is the brightness emitted by a display per unit area, measured in cd/m^2. To quantify that on a monitor, a photometer is used because it is designed to measure the light output of a surface and provide a direct reading of luminance. A lux meter measures illuminance—how much light falls on a surface—not the display’s own brightness, so it doesn’t reflect luminance accurately. A goniometer is used to analyze how light is distributed at different angles, which isn’t about a single luminance value. A colorimeter focuses on color characteristics and typically isn’t the best tool for precise luminance measurement. So, for measuring a monitor’s luminance, the photometer is the appropriate instrument.