photo credit vs acknowledgment

photo credit and acknowledgment both are nouns.

Word	Noun	Adjective	Verb	Adverb
photo credit	Yes	No	No	No
acknowledgment	Yes	No	No	No

As nouns, acknowledgment is a hypernym of photo credit; that is, acknowledgment is a word with a broader meaning than photo credit:

photo credit: a note acknowledging the source of a published photograph
acknowledgment: a short note recognizing a source of information or of a quoted passage

Other hypernyms of photo credit include citation, cite, credit, mention, quotation, reference.

photo credit (noun)	acknowledgment (noun)
a note acknowledging the source of a published photograph	a statement acknowledging something or someone
	a short note recognizing a source of information or of a quoted passage
	the state or quality of being recognized or acknowledged