brightness level vs luminousness

brightness level and luminousness both are nouns.

Word	Noun	Adjective	Verb	Adverb
brightness level	Yes	No	No	No
luminousness	Yes	No	No	No

As nouns, brightness level and luminousness are synonyms defined as:

brightness level and luminousness: the quality of being luminous; emitting or reflecting light

Other synonyms of brightness level include brightness, light, luminance, luminosity.

brightness level (noun)	luminousness (noun)
the quality of being luminous; emitting or reflecting light	the quality of being luminous; emitting or reflecting light