brightness vs brightness level

brightness and brightness level both are nouns.

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

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

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

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

brightness (noun)	brightness level (noun)
the location of a visual perception along a continuum from black to white	the quality of being luminous; emitting or reflecting light
the quality of being luminous; emitting or reflecting light
intelligence as manifested in being quick and witty