If I take a photograph of another work that is in the public domain, can I apply a CC license to my photo?

Answer:

That depends. You can apply a CC license to your photograph if your photograph constitutes a work of original authorship, a question that varies by jurisdiction. As a general matter, your photograph must involve some creative choices, such as background setting, lighting, angle, or other mark of creativity. In the United States, an exact photographic copy of a public domain work is not subject to copyright because there is no originality (even if there is effort or “sweat” exerted in its creation).

In practice, if your photograph is sufficiently creative to attract copyright protection, people will likely have to comply with the license conditions if they reproduce your entire photograph in verbatim form, absent some applicable exception or limitation such as fair use. However, they would not have to comply with the license conditions if they reproduce only those parts of the work in the public domain. This is because your copyright in the adaptation only extends to the material you contributed, not to the underlying work.