pitch blackness vs blackness

pitch blackness and blackness both are nouns.

Word	Noun	Adjective	Verb	Adverb
pitch blackness	Yes	No	No	No
blackness	Yes	No	No	No

As nouns, pitch blackness and blackness are synonyms defined as:

Other synonyms of pitch blackness include black, lightlessness, total darkness.

pitch blackness (noun)	blackness (noun)
total absence of light	the quality or state of the achromatic color of least lightness (bearing the least resemblance to white)
	total absence of light