page_title: Four Thirds system
section_title: Micro Four Thirds System
hierarchical_section_title: Four Thirds system / Micro Four Thirds System
caption_attribution_description: English: Olympus Micro Four Thirds Concept Model at the E-30 Fair in Tokyo.
context_page_description: The Four Thirds System is a standard created by Olympus and Eastman Kodak for digital single-lens reflex camera and mirrorless camera design and development.
  The system provides a standard that, with digital cameras and lenses available from multiple manufacturers, allows for the interchange of lenses and bodies from different manufacturers. U.S. Patent 6,910,814 seems to cover the standard. Proponents describe it as an open standard, but companies may only use it under a non-disclosure agreement.
  Unlike older single-lens reflex systems, Four Thirds was designed from the start to be entirely digital. Many lenses are extensively computerised, to the point that Olympus offers firmware updates for many of them. Lens design has been tailored to the requirements of digital sensors, most notably through telecentric designs. The size of the sensor is significantly smaller than for most DSLRs and this implies that lenses, especially telephoto lenses, can be smaller. For example, a Four Thirds lens with a 300 mm focal length would cover about the same angle of view as a 600 mm focal length lens for the 35 mm film standard, and is correspondingly more compact.
context_section_description: In August 2008, Olympus and Panasonic introduced a new format, Micro Four Thirds.
  The new system uses the same sensor, but removes the mirror box from the camera design. A live preview is shown on either the camera's main liquid-crystal display or via an electronic viewfinder, as in digital compact cameras. Autofocus may be accomplished via a contrast detection process using the main imager, again similar to digital compact cameras. Some Olympus manufactured camera bodies also feature phase detection auto focus built into the sensor. The goal of the new system was to allow for even smaller cameras, competing directly with higher-end point-and-shoot compact digital cameras and DSLRs.  The smaller flange focal distance allows for more compact normal and wide angle lenses. It also facilitates the use, with an adapter, of lenses based on other mounting systems, including many manual focus lenses from the seventies and eighties.
  In particular, Four Thirds lenses can be used on Micro Four Thirds bodies with an adapter, however, "all of the functions of the Micro Four Thirds System may not always be available."
caption: Concept Micro Four Thirds camera by Olympus
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