[9.3] This term can be used in two different ways.

In flux transfer, it is the density of luminous flux leaving a surface within an enclosure before interreflections occur.  Note: For light sources, this is the luminous exitance as defined in this document. For non-self-luminous surfaces, it is the reflected luminous exitance of the flux received directly from sources within the enclosure or from daylight.

In lighting calculations, it is the total exitance at time zero before depreciation (light loss) occurs.

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