My younger sister is a musician and I was her producer (I made 2,000 copies of a 45 RPM record for her) so I studied copyright at that time in order to know what I was doing. Copyright is automatic and you don't need to do anything. However, in order to PROVE ownership of a copyright, you need to have evidence of initial ownership! What we did was to wrap a tape recording or other form of proof of work, address it to myself and take it to the post office and have them stamp the wrapper with the date as proof of time. As long as the wrapper is intact, any challenge of copyright ownership can be proven by bringing the intact object to court and opening it there as proof of ownership. From that point on, the court documents will be the proof. This will work for pictures too.

I know you asked the question a year ago, but I only saw it now. Perhaps the answer still has value to someone.