The Truth About Digital Cameras?

This is rather pixling? David Pogue ran a test for his show "It's All Geek to Me" on Discovery.

He took a 13 megapixel photo, down rezzed it twice to 8 and 5 megapixels, and then blew them all up to 16x24 prints. He took the prints to the streets of New York and had people see if they could tell the difference...