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The EF 50mm lenses are a group of normal prime lenses made by Canon that share the same focal length. These lenses are based on the classic double-Gauss lens,〔http://www.canon.com/camera-museum/camera/lens/ef/data/standard/ef_50_18ii.html?p=1 〕 with the f/1.8 being a standard six-element double-Gauss with an air gap and powers between element 2 and 3〔() 〕 and its faster cousins adding additional elements.〔() 〕 The 50mm focal length, when used with a 35mm film or full-frame sensor, has been widely considered to match the perspective seen by the human eye.〔(50mm and the Human Eye ), ''Gary Voth''. Retrieved 2011-01-10.〕 Canon 50mm lenses have an EF type mount that fits the Canon EOS line of cameras. When pairing a 50mm lens to a Canon DSLR with an APS-C sized sensor, the crop factor effectively turns the 50mm focal length into a 80mm field of view. Seven EF 50mm lenses have been sold by Canon: * 1.0L USM (discontinued, replaced by 1.2L USM) * 1.2L USM * 1.4 USM * 1.8 (discontinued, replaced by 1.8 II) * 1.8 II * 1.8 STM * 2.5 Compact Macro ==EF 50mm 1.0L USM== The discontinued EF 50mm 1.0L USM is a professional L series autofocus lens. On the used market sells for as much as double the original retail value. It was the fastest SLR lens in production during its lifetime.〔 This lens has a metal body and mount, and plastic extremities. It also features a wide rubber focus ring that is damped, a distance window with infrared index, and the ability to set the focus range from 0.6m to infinity, or 1m to infinity. In common with the EF 85mm f/1.2L USM it uses an electronic "focus by wire" system and requires power from the camera in order to manual focus. The 8-blade diaphragm and maximum aperture of 1.0 give this lens the ability to create extremely shallow depth of field effects and to support low light situations. The optical construction of this lens contains 11 lens elements, including two ground and polished aspherical lens elements. This lens uses a floating front extension focusing system, powered by a ring-type USM motor. The front of the lens does not rotate, but does extend when focusing. Despite its price and large maximum aperture, the 1.0L was not a particularly sharp lens at any aperture, and the two cheaper 50mm options offered far better sharpness when stopped down beyond about 2.8.〔(【引用サイトリンク】title=Review of the Canon EF 50mm f/1.0L USM Lens, EF 50mm f/1.4 USM lens, and EF 50mm f/1.8 II Lens )〕 This, combined with the high production cost and low sales volume, led to it being discontinued in 2000 and eventually superseded by the 1.2 edition. 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「Canon EF 50mm lens」の詳細全文を読む スポンサード リンク
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