Luminance Converter

About Luminance

Luminance is the amount of light emitted, reflected, or transmitted from a surface in a given direction. It is extremely critical in visual perception, screen design, and standards for lighting.

• Candela per square meter (cd/m²) – SI unit of luminance, also known as a nit.
• Kilocandela / Millicandela per m² – Larger or smaller luminance measurement scales.
• Foot-lambert (fL) – Common in US display and cinema calibration.
• Lambert (L) – Outdated unit, equal to π cd/cm².
• Stilb (sb) – CGS unit of luminance, equal to 10,000 cd/m².
• Apostilb (asb) – Dated CGS unit, 1 asb ≈ 0.3183 cd/m².
• Candela per square foot / inch – Used in imperial unit systems.

Luminance Units

Luminance is a photometric term that is employed to quantify the brightness of a surface to the human perception. It is a measure of the luminous intensity emitted or reflected from a surface in a particular direction and typically per unit area. These types of units are critical in fields like display technology, lighting design, photography, astronomy, and vision science.

Common Luminance Units

• Candela per square meter (cd/m²) – This is the SI unit of luminance and also referred to as a nit (nt) in the context of the display. A candela of luminous intensity distributed over an area of one square meter, it is used widely to quantify screen brightness and light quality.
• Kilocandela per square meter (kcd/m²) – Similar to 1,000 cd/m², it is used when defining extremely bright sources, such as high-performance LED display screens or daylight simulators.
• Millicandela per square meter (mcd/m²) – Used for very low-level displays or surfaces, generally where 1/1,000 candela per square meter is utilized, such as in low-light environments or in scientific devices.
• Nit (nt) – A non-SI unit for cd/m², frequently found in consumer goods, especially TVs, monitors, and smartphones. For example, a smartphone display will be described to have 1,200 nits of brightness.
• Stilb (sb) – A CGS (centimeter-gram-second) unit, where 1 stilb = 10,000 cd/m². It is rarely used in modern applications but can be encountered in historical and theoretical contexts.
• Apostilb (asb) – An outdated, non-SI unit of luminance equivalent to 1/π candela per square meter (~0.318 cd/m²). It was used in certain older photometry literature and vision science.
• Lambert (L) – Another CGS unit, with 1 lambert = 10⁴/π cd/m² (~3,183 cd/m²). It expresses a perfectly diffusing surface's luminance value reflecting or emitting light.
• Foot-lambert (fL) – Common in the U.S. movie industry and projector brightness ratings, 1 foot-lambert = 1/π candela per square foot (~3.426 cd/m²). It is widely used in theatre and display visual performance specifications.
• Candela per square foot (cd/ft²) – Unit of luminous intensity per square foot, utilized in architectural lighting in the imperial system of measurement.
• Candela per square inch (cd/in²) – Used for very small, high-luminance areas, like in microdisplays or sophisticated apparatus. This unit is closer to a true understanding of luminance with small, concentrated light sources.

Why Luminance Units Matter