It is interesting to note that if you live in the United States, you must formally register your copyright with the government if you intend to pursue litigation against anyone for copyright infringement. In Canada, and everywhere else in the world, this is not applicable.
In photography, the second you press the shutter button you own the copyright for the image that is taken. It is an international right that has been in place since 1886. For more information feel free to visit the Wikipedia entry on copyright.