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