What is Child Pornography?
Knowingly possessing, producing or trafficking in images of actual children engaged in sexual activity is a crime under both state and federal law. Federal law defines anyone under 18 as a child for these purposes. Under New York law, possession of a "sexual performance by a child" under 16 is a felony; promotion of a sexual perfomance by a child under 17 is also a felony. The First Amendment provides protection to defendants, but only where no actual child is involved in the production of the image. Images of actual children, even morphed images of real children, are not protected by the First Amendment.
At the same time, because of the First Amendment issues, child pornography offenses are not "strict liability" like statutory rape: in order to be convicted, the defendant must know the material involved the actual abuse of a child. In most cases, though, that can be proven easily if the photograph is realistic and depicts a young child. While state laws vary, the Department of Justice publishes a Citizen's Guide to U.S. Federal Law on Child Pornography, which is available here.