Look at it this way. In the most straightforward case, if you sneak into someone's house and take a picture of them when they're naked, clearly the fact that you own the camera doesn't mean you own the right to distribute such a picture. The person whose picture is being taken didn't consent. Now, let's take a case where the person consents to the picture. Does that consent to have a picture being taken implicitly grant the right to distribute those pictures? At a minimum, it would depend on the facts. A picture taken of someone posing for a picture in front of a fancy restaurant with a bunch of friends, you could argue the right to redistribute was implied in that consent, and certainly it's not really practical to get a signed consent form of all the people in the picture. Nude photos taken in a private bedroom? You can be damned sure that consent to have the picture taken did not carry with it the right to redistribute unless that was explicit (and as the person doing the redistribution you would probably need it to be in writing to cover your ass).