Why even put it on your work?
This from -
http://www.copyright.gov/help/faq/
"When is my work protected?
Your work is under copyright protection the moment it is created and fixed in a tangible form that it is perceptible either directly or with the aid of a machine or device."
The "C" is not necessary. Your photo had it when you snapped it. Perhaps the "C" may be a "scarecrow" for the amateur thief. But if you are concerned about it being stolen and used commercially and you take it to court, then your work needs to be registered.
Tom