I just found this:
Photographer's Copyright on artwork reproductions
Michael Greenhalgh has a very interesting webpage explaining Copyright on various types of Art Objects: There may be two copyrights: copyright in the artistic work (for example, a painting) and copyright in the photograph of the artistic work). You will generally need permission from the owner of copyright in the artistic work unless the copyright has expired. It is unlikely you need permission in relation to the photograph, if the photograph depicts nothing but the artistic work and is indistinguishable from other photographs of the same work. Otherwise, you will generally need permission from the owner of copyright in the photograph.
In other words, when someone photographs a painting of Van Gogh in a museum, producing a picture that is indistinguishable from other photographs of the same work, this cannot be considered an original art creation: it is precisely requested that the photographer annihilate his own personality to only mirror the artist's own personality and reflect the artwork with maximum fidelity through the photograph. Thus, the photographer does not hold any copyright on the picture itself.
Of course, the above can only be proven right by going into court and feeding an army of lawyers to nitpick over the interpretation of local laws. And even then, this would only apply to a specific country or jurisdiction, so it would have to be restarted all over again elsewhere. To be on the safe side, the WebMuseum requests that photographers contributing pictures to the WebMuseum agree to transfer all of their rights to the WebMuseum curator.