ft-l
Definition
Noun: - Foot-lambert: A former unit of luminance, representing the brightness of a surface that emits or reflects one lumen of light per square foot. It was used to measure the intensity of light as perceived by the human eye from a surface.
Usage
The term 'ft-L' is an abbreviation for 'foot-lambert'. It is used in technical and historical contexts related to photometry (the science of measuring visible light). - The old cinema screen had a luminance of approximately 12 ft-L. - This measurement, given in foot-lamberts, is now largely obsolete.
Advanced Usage
- Technical Specification: While obsolete in modern scientific contexts, 'ft-L' may still be encountered in older technical documents, manuals for legacy display equipment (like certain projectors or CRTs), or in historical analyses of lighting and display technologies.
- Conversion: One foot-lambert (1 ft-L) is equal to approximately 3.426 candelas per square meter (cd/m²), which is the modern SI unit for luminance.
Variants and Related Words
- Footlambert: An alternative spelling for the same unit.
- Lambert (L): A related, but different, unit of luminance. One lambert is equal to 1/π candelas per square centimeter. The foot-lambert is 1/π candelas per square .
- Luminance: The photometric measure of the luminous intensity per unit area of light travelling in a given direction. It describes the amount of light that passes through, is emitted from, or is reflected from a particular area.
Synonyms
- Footlambert: The full term for the abbreviation 'ft-L'.
- (No direct conceptual synonyms, as it is a specific, named unit of measurement.)
Related Phrases
- Candelas per square meter (cd/m² or nit): The modern SI unit that has largely replaced the foot-lambert for measuring luminance.
- Apostilb (asb): Another obsolete unit of luminance; 1 apostilb = (1/π) cd/m².
Noun
-
a former luminance unit equal to one lumen per square foot
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