Luminance is a photometric measurement that quantifies the brightness of a surface or an object as perceived by the human eye. It is an important concept in lighting, display technology, and image processing. Luminance is typically expressed in units of candela per square meter (cd/m²) in the International System of Units (SI). Here are some key points about luminance:
1.Brightness Perception: Luminance represents the amount of visible light emitted or reflected by a surface or object and how our eyes perceive that brightness. It is related to the intensity of light that enters our eyes from a particular direction.
2.Units: Luminance is measured in candela per square meter (cd/m²), which is equivalent to nit (nt) or foot-lambert (fL) in non-SI units. One candela per square meter is equal to one nit.
3.Directional Sensitivity: Luminance takes into account the sensitivity of the human eye to light at different angles. It gives more weight to light coming from a source in the direction of the observer’s gaze.
4.Luminance vs. Illuminance: Luminance and illuminance are related but distinct concepts. Illuminance (measured in lux or foot-candles) quantifies the amount of light falling on a surface, while luminance quantifies the brightness of the surface itself.
5.Applications: Luminance is essential in various fields, including:
（1）Display Technology: Luminance is used to specify the brightness of screens, monitors, and displays, such as LED TVs, computer monitors, and smartphone screens.
（2）Lighting Design: Luminance is a key parameter in architectural and interior lighting design. Designers use it to ensure that spaces are adequately and uniformly lit.
（3）Photography and Imaging: In photography and image processing, luminance is a component of the perceived brightness of an image. It is used in techniques like high dynamic range (HDR) imaging.
（4）Visual Perception: Luminance plays a role in human visual perception, influencing how objects and scenes appear to our eyes.
6.Measurement Techniques: Luminance can be measured using specialized instruments called luminance meters or photometers. These devices capture the intensity of light from a surface at various points and calculate the average luminance.
7.Brightness Levels: Luminance values can vary significantly depending on the surface or object being measured. For example, a typical computer monitor may have a luminance of around 250 to 350 cd/m², while outdoor sunlight can have luminance levels well above 10,000 cd/m².
8.Contrast: Luminance contrast refers to the difference in luminance between adjacent areas or objects in an image or scene. It is a critical factor in visual perception and image quality.