Pictures with pictures in them

[Fribble]

I understand that the person who takes a picture or creates an original work automatically owns the copyright to it.

I would assume taking a picture of somebody else's original work just so you can get the content of the original is a no-no, though I have seen this done with original paintings and sculptures so I don't know for sure.

Where is the line with pictures that have copyrighted material in them? A photograph of someone's original artwork or a picture of a room or museum hallway that contains art or pictures on the walls. Can someone clarify this for me? What rules define infringement with materials like this?

:)