It is true that you can gain a copyright on creative and original elements added to public domain works, even when the underlying original public domain works remain in the public domain for anyone else to use.
You can also get a copyright on a compilation of public domain works, even when the underlying original public domain works that make up the compilation remain in the public domain for anyone else to use.
You can also record a transfer of copyrights with the Copyright Office of all of the copyrights in the photographs taken by the person or persons from whom you inherited them. You must show how the transfer was made (ie, by will, by intestate succession).
You cannot, however, get a copyright for the underlying public domain photo taken by someone other than the person from whom you inherited it. For example, the copyrights in a professionally-shot photograph now in the public domain was taken by a photographer named Mr. X. The photograph's copyright can now belong to anyone specifically named in Mr. X's will or to Mr. X's heirs. YOU, however, cannot claim the copyright in the underlying public domain photograph taken by Mr. X unless you were named in his will or you are one of Mr. X's heirs.
You can only gain a copyright in someone else's work that is now in the public domain by adding original and creative elements to the work. The copyright will cover the added creative elements but not the underlying public domain work.
You can check out the Ted Turner colorized, public domain black and white movies for an example of what in an altered public domain work can be copyrighted. While the black and white movies remain in the public domain, Turner holds the copyright in the colorized versions.
For more information on copyrights and public domain materials and on transfer of rights and inherited copyrighted works, you can visit the official government website at:
http://www.copyright.gov. Review, specifically, Circular 1, "Copyright Basics," Section "Who Can Claim Copyright."
