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The Extender EF lenses are a group of teleconverter lenses made by Canon. These lenses are used between any compatible EF type lens and any of the Canon EOS line of cameras. When used with a compatible lens, they will multiply the focal length of the lens by a factor of either 1.4× or 2.0×, at the cost of decreasing the lens' aperture by 1 or 2 stops respectively. For example, using a 1.4× or 2.0× extender with the Canon EF 500mm 4L IS USM would result in a 700mm 5.6 or 1000mm 8 lens. Canon has released six models: * 1.4× * 1.4× II * 1.4× III * 2× * 2× II * 2× III ==Technical information== The extenders are constructed with metal bayonets, and engineered plastic ends. There are no moving parts, other than the lens latch lock. Three generations of the extenders exist: the older 1.4× and 2×, the 1.4× II and 2× II, and the 1.4× III and 2.0× III. The II versions have weather-sealing and anti-reflective surfaces inside the extender body. The optical construction of the 1.4× versions are a of five-element design. Both 2× versions use seven elements, although the optical formula of the II version is different, to improve optical performance. The III versions of the extenders have improved autofocus performance as well increased image quality over the II, and their front and rear elements are coated with fluorine anti-smear coating to be easier to clean. 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 Extender EF」の詳細全文を読む スポンサード リンク
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