What is non-luminance?

Answer 1

The non-luminous is those objects which do not produce its own light.It provide the light which is reflecting from another e.g.moon did not produce its own light,sun is giving the light to moon,moon reflecting the light of sun.

Answer 2

Non-luminance refers to objects or surfaces that do not emit light on their own, but instead reflect light from another source. This term is often used in discussions of lighting, Photography, and vision science to differentiate between light-emitting and light-reflecting elements.