While digital photography and image-editing software have brought about an increased awareness of the degree to which camera images can be manipulated, the practice of doctoring photographs has existed since the medium was invented.
Faking It: Manipulated Photography Before Photoshop at The Metropolitan Museum of Art is the first major exhibition devoted to the history of manipulated photography before the digital age. Featuring some 200 visually captivating photographs created between the 1840s and 1990s in the service of art, politics, news, entertainment, and commerce, the exhibition offers a provocative new perspective on the history of photography as it traces the medium’s complex and changing relationship to visual truth.

The photographs in the exhibition were altered using a variety of techniques, including multiple exposure (taking two or more pictures on a single negative), combination printing (producing a single print from elements of two or more negatives), photomontage, overpainting, and retouching on the negative or print.

In every case, the meaning and content of the camera image was significantly transformed in the process of manipulation.

http://www.metmuseum.org/about-the-museum/press-room/exhibitions/2012/faking-it
http://blogs.adobe.com/photoshopdotcom/2012/10/faking-it-manipulated-photography-before-photoshop.html