Illuminance

In photometry, illuminance is the total luminous flux incident on a surface, per unit area. It is a measure of how much the incident light illuminates the surface, wavelength-weighted by the luminosity function to correlate with human brightness perception. Similarly, luminous emittance is the luminous flux per unit area emitted from a surface.

Luminous emittance is also known as luminous exitance.

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Source: Wikipedia · Image: Wikimedia Commons · CC BY-SA 4.0

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