Manipulated Photography Before Photoshop
If you're going to be in NYC during the holiday season (a great time to visit 'shoot' Gotham) be sure to check out the MET Museum's exhibit focusing (forgive the pun) on photo manipulation pre-Photoshop.
A video is available at http://www.metmuseum.org/exhibitions/listings/2012/faking-it
Further reading at http://www.thesmartset.com/article/article11141201.aspx
The exhibit runs through 1/27/13