Here are some info sheets on copyright from the Copyright Council of Australia.
Scroll down to P for "Photographer" G011
http://www.copyright.org.au/publications/infosheets.htm
Basically whoever physically takes the photo automatically and without the need for registration, has copyright on it and in most cases being in the so called "public domain" does not automatically give anyone else rights to use that photo without permission. A copyright notice on the image is not required either.
Anyway it is interesting read I recon
Mike