Define the term Luminance
Luminance refers to the perceived brightness of an object or a surface, typically in the context of human vision or digital imaging. It is a measure of the intensity of light emitted or reflected by a surface per unit area in a specific direction. Luminance is a fundamental concept in fields such as physics, optics, photography, and computer graphics, where it plays a crucial role in describing and quantifying the brightness of light sources and illuminated objects.
Key Points about Luminance:
-
Physical Definition: Luminance LLL is defined as the luminous flux Φ\PhiΦ per unit solid angle Ω\OmegaΩ per unit projected area AAA of a source or surface: L=ΦΩ⋅AL = \frac{\Phi}{\Omega \cdot A}L=Ω⋅AΦ?
- Units: Luminance is typically measured in candelas per square meter (cd/m²).
-
Perceived Brightness: Luminance correlates with the subjective perception of brightness by the human eye. Higher luminance values correspond to brighter perceived light.
-
Relationship with Illuminance: Luminance differs from illuminance, which measures the total amount of light falling on a surface. Luminance specifically describes how bright the surface appears when viewed from a particular angle.
-
In Digital Imaging: In digital imaging and computer graphics, luminance refers to the grayscale intensity of a pixel, often represented as a value between 0 (black) and 1 (white) or in a range (e.g., 0-255) depending on the bit depth.
-
Applications:
- HDR Imaging: High Dynamic Range (HDR) imaging uses luminance values to represent a wide range of brightness levels in scenes.
- Display Technology: Luminance is crucial in determining the brightness and contrast capabilities of displays, such as LCD monitors and OLED screens.
- Colorimetry: In color science, luminance is used to calculate color spaces and to define relationships between light sources and perceived colors.
-
Mathematical Representation: In color spaces like CIELAB or CIELUV, luminance is often represented as YYY, which represents the perceived brightness component of a color.
Understanding luminance is essential for accurately representing and manipulating light and brightness in various fields, ensuring accurate visual perception and reproduction in imaging and display technologies.
