dimness vs indistinctness

dimness and indistinctness both are nouns.

Word	Noun	Adjective	Verb	Adverb
dimness	Yes	No	No	No
indistinctness	Yes	No	No	No

As nouns, indistinctness is a hypernym of dimness; that is, indistinctness is a word with a broader meaning than dimness:

Other hypernyms of dimness include blurriness, fogginess, fuzziness, softness.

dimness (noun)	indistinctness (noun)
the property of lights or sounds that lack brilliance or are reduced in intensity	the quality of being indistinct and without sharp outlines
the quality of being dim or lacking contrast
the state of being poorly illuminated