The FourThirds mount is a lens mount designed by Olympus and Kodak for digital-only single-lens reflex cameras and announced in 2001. It is designed for 4:3 aspect ratio sensors measuring 17.3 \u00d7 13mm, with a crop factor of 2\u00d7. It is a bayonet mount with three tabs, a focal flange distance of 38.67mm and a throat diameter of 43.26mm. Communication is entirely electronic; there are no mechanical linkages between the lens and the camera.<\/p>\n\n\n\n
The FourThirds lens mount was designed to be an open standard for multiple manufacturers, with seven manufacturers joining the standard. Only three\u2014Olympus, Panasonic, and Leica\u2014have produced bodies, and four\u2014the original three plus Sigma\u2014have made dedicated FourThirds lenses. Earlier cameras used Kodak CCD sensors, and later models switched to Panasonic NMOS sensors.<\/p>\n\n\n\n
Note:<\/mark><\/strong> This reference currently counts only autofocus lenses.<\/p>\n\n\n\n Jump to: Olympus Zuiko Digital<\/a><\/strong>, Leica D<\/a><\/strong>, Sigma<\/a><\/strong> lenses; Adapters<\/strong><\/a>, Compatibility<\/strong><\/a>.<\/p>\n\n\n\n Zuiko Digital lenses are divided into three tiers\u2014standard, High Grade, and Super High Grade. Optical and build quality are progressively better on HG and SHG lenses, and that also reflects on the size, weight, and price. HG and SHG lenses are dust and moisture-sealed, have a focus distance scale, and almost all have internal focusing.<\/p>\n\n\n\n Leica-branded lenses have an aperture ring and image stabilization \u2013\u200d all except one for each. Both the aperture ring and the image stabilization are usable only on Panasonic and Leica cameras; aperture rings do nothing on Olympus cameras.<\/p>\n\n\n\n Sigma lenses were available for other mounts; no lens was specifically designed for the FourThirds system. EX lenses have a better build quality and external finish. DG lenses were designed for a full 35mm sensor (“full-frame”), while DC lenses are designed for APS-C sensors.<\/p>\n\n\n\n Official FourThirds to microFourThirds adapters.<\/p>\n\n\n\n FourThirds lenses are fully compatible with microFourThirds cameras when used with adapters that pass through electronic contacts, like Olympus MMF-series and Panasonic DMW-MA1 adapters. Aperture control is retained; autofocus is officially supported with Olympus and Panasonic lenses on all cameras except Panasonic G1, GH1, and GF1, but since microFourThirds mostly uses contrast-detect autofocus, its speed is often questionable. Autofocus with Sigma FourThirds lenses is officially not supported, but in practice, it depends on the lens and camera combination \u2013\u200d some cameras will hunt less, some more, or even give up with some lenses. Cameras with phase-detect sensors (Olympus E-M1\/OM1 series, some E-M5\/OM5 models, and Panasonic G9 II) will autofocus all FourThirds lenses without issues, but the speed is not always the same as on the latest native-mount FourThirds cameras.<\/p>\n\n\n\n Finally, there are some FourThirds lenses that support contrast-detect autofocus (CDAF), with or without a firmware upgrade. Even with full CDAF support, autofocus operation usually isn’t as fast as on native-mount cameras. Here’s the list of supported lenses.<\/p>\n\n\n\nOlympus Zuiko Digital lenses<\/h2>\n\n\n\n
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Leica D lenses<\/h2>\n\n\n\n
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Sigma lenses<\/h2>\n\n\n\n
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microFourThirds adapters<\/h2>\n\n\n\n
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Compatibility<\/h2>\n\n\n\n
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