illuminance vs brightness level

illuminance and brightness level both are nouns.

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

As nouns, brightness level is a hypernym of illuminance; that is, brightness level is a word with a broader meaning than illuminance:

illuminance: the luminous flux incident on a unit area
brightness level: the quality of being luminous; emitting or reflecting light

Other hypernyms of illuminance include brightness, light, luminance, luminosity, luminousness.

illuminance (noun)	brightness level (noun)
the luminous flux incident on a unit area	the quality of being luminous; emitting or reflecting light