Understanding Luminance
Luminance is a photometric measure that quantifies the luminous intensity per unit area of light traveling in a given direction. Essentially, it describes how much light is emitted or reflected from a particular surface, as perceived by the human eye. It is measured in candelas per square meter (cd/m²), also known as nits.
Key Principles of Luminance
Unlike luminous flux (total light emitted) or illuminance (light falling on a surface), luminance focuses on the light emitted or reflected *from* a surface *towards* the observer. It takes into account the area of the surface and the solid angle of emission, making it a crucial indicator of perceived 'brightness' or 'glow' in a specific viewing direction. Surfaces with high luminance appear brighter to the eye.
Practical Examples of Luminance
A common example of luminance is the brightness setting on a television or smartphone screen. When you increase the 'brightness,' you are typically increasing the luminance of the display. Another example is the light reflected off a white sheet of paper under bright illumination; the paper's luminance is what makes it appear white and bright to your eyes from different angles.
Importance and Applications
Luminance is vital in many fields, including display technology (e.g., specifying screen brightness for monitors, TVs, and virtual reality headsets), lighting design (ensuring comfortable and effective illumination in spaces), and vision science (studying how the human eye perceives light and brightness). It ensures that visual environments are optimally designed for clarity, comfort, and safety.