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The Sigma SA-mount is a lens mount by the Sigma Corporation of Japan for use on their autofocus single-lens reflex cameras. It was introduced with the ''SA-300'' in 1992. Originally, the SA-mount was a dual-bayonet mount with inner (SA-IB) and outer (SA-OB) bayonets, the latter being a feature intended to mount heavy telephoto lenses,〔SA-300 owner's manual〕 but never utilized by Sigma and consequently dropped with the release of the ''SD14'' in 2007. There were two precursors to the introduction of SA-mount cameras, the manual-focus Sigma Mark-I in 1976, which still featured a M42 screw lens mount, and the ''SA-1'' of 1983 with Pentax K-mount. Mechanically, the (inner) SA-mount is similar to the Pentax K-mount as well,〔(【引用サイトリンク】title=Comparison: Sigma SA mount vs. Pentax K )〕 but with a flange focal distance of 44.00 mm, identical to that of the Canon EF-mount. Like the EF-mount, the SA-mount uses electrical communication between body and lens, and in fact uses the same signalling lines and protocol as the EF-mount, despite the physical incompatibility. Sigma has long produced EF-mount lenses for Canon cameras, and thus had the ability to use this protocol. All Sigma SLRs and DSLRs can use manual focus lenses too, which have no electrical communication between body and lens. == Compatibility == M42-mount lenses can be mounted via adapters utilizing the SA inner bayonet. As a result of the physical similarities Pentax K-mount (PK) lenses can be fitted straight onto the SA-mount as well, once the protruding AA lever and AA protector outcrop are removed, though the fit is slightly loose as the SA-mount has a slightly bigger bore than the PK-mount. However, due to the difference in registration distance scale focusing isn't possible and the close focusing capabilities will be reduced. Utilizing the SA-OB bayonet mount (on camera bodies supporting it), Nikon F-mount can be fitted and used via a JTAT mount adapter developed by Kazuo Suzuki, Tachibana Seisakusho.〔http://www.jtat.com/sd/sd_main/SD_Nikon.html〕 In digital cameras, it is important to make sure that the rear of an adapted lens never hits the camera's dust protector filter when focused to infinity. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Sigma SA-mount」の詳細全文を読む スポンサード リンク
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