It's the only Cinematography credits on the disc. Yes or no to credit?

I agree with Corey... I wouldn't add it.

Context should not matter as far as the online database is concerned. Either it's a valid crew job per the rules, or it isn't.

For my local database, I would look at the context. If it was indeed the sole cinematography-related credit in the entire film, I'd probably enter him into my local database using the non-contributable custom crew field. Before doing so, I would also take a look at the person's other credits around that time: how was he credited in the films he worked on right before and right after this one? While not conclusive, that does help to paint a picture of whether I consider his work worthy of inclusion in my local database. But the "best" outcome would still be that I entered him using the non-contributable custom crew field - even with all the context in the world, under the current rules "Principal Camera" would not qualify for a "Cinematography" or a "Director of Photography" credit.