Although not really an open-source initiative, (and more of consumer hardware concern), some of the biggest names in digital cameras (Olympus, Kodak, Sanyo, Sigma and Fujifilm, Panasonic) have signed Joint Development Agreements to develop 'Interchangeable Lens Type Digital SLR Cameras.'
http://www.four-thirds.org/en/index.html
"The Four Thirds System uses a Four Thirds-type image sensor, which makes it possible for manufacturers to design extremely compact lenses that combine high mobility and handling ease with the optical characteristics needed to maximize sensor performance. In addition, the Four Thirds System defines an open standard for lens mounts that benefits consumers by assuring compatibility between Four Thirds System bodies and lenses produced by manufacturers that adhere to the standard. The Four Thirds System standard was first announced in September 2002 by Olympus Corporation and Eastman Kodak Company of the United States, and is currently also supported by Fuji Photo Film Co, Ltd., Sanyo Electric Co., Ltd., Panasonic, and Sigma Corporation."
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