For you kids out there, he's referring to developing a roll of film- something cameras used to use to capture images. Developing is a chemical process whereby the latent image stored on the film by the camera is made visible, usually in negative form (inverted colors or black/white), which then gets projected onto a piece of specially treated paper to produce a photograph.
On Thursday, November 1, 2012 3:54:29 PM UTC-5, Kevin Crowley wrote:
http://www.sheldoncomics.com/strips/sd121026.png