Short of getting answers from a lawyer specializing in copyright issues (which I’m definitely not), I think that the best source of authoritative information about copyright law is the Copyright Office of the Library of Congress (www.copyright.gov).
It’s my understanding that current copyright law provides for the copyright to any photographic image (including prints, negatives, slides and, presumably, digital images) to remain with the creator (photographer) for 100 years unless specifically transferred to another person or entity.
If I’m correct on this, photos taken before 1912 would be “fair game” for copying, but anything more recent may not be. If the photographer is deceased his/her copyright would devolve to her/his estate, but would not cease to exist until that 100 year period of protection had elapsed.
There were in the past, and there may still be at present, provisions for renewal of a copyright, so it may not be entirely safe to assume that anything more than a century old is automatically in the public domaine.
I’m absolutely sure that copyright does not automatically transfer with th sale or donation of an image, unless (A) the seller or donor owns the copyright in the first place and ( the transfer of copyright, as well as the transfer of the physical image, is specifically mentioned in the bill of sale or deed of gift.
But don’t take my word for it! Go to the Copyright Office web site and get authoritative information from folks who are paid (with your tax money)to provide it.