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The Canon EF 24–70 mm lens is a family of professional EF mount wide-to-normal zoom lenses manufactured and sold by Canon. The first of the family, the EF 24–70 mm f/2.8L, was introduced in 2002 to replace the well-regarded 28–70mm f/2.8L. Two later versions were announced in 2012. The first of these, the EF 24–70 mm f/2.8L II, was announced by Canon in February,〔(Canon EF 24-70 f/2.8L II Announced « Canon Rumors ). Canonrumors.com (2012-02-07). Retrieved on 2013-10-04.〕〔(Canon EF 24-70 f/2.8L Version 1 vs Version 2 « Canon Rumors ). Canonrumors.com (2012-02-07). Retrieved on 2013-10-04.〕〔(Canon EF 24-70 f/2.8L II « Canon Rumors ). Canonrumors.com (2012-02-06). Retrieved on 2013-10-04.〕 but would not ship to customers until September of that year. This lens replaced the Mk I, and had an MSRP of US$2299 when introduced.〔 The latest member of the family is the EF 24–70 mm f/4L IS USM, which became available in January 2014. The f/4 version, which is the first of the family to include image stabilization, was initially reported to be the standard kit lens for the Canon EOS 6D, but did not appear in 6D kits in most markets until late 2014. Like its predecessor, the f/2.8 Mk I lens was often considered to have excellent contrast, color rendition and decent sharpness wide open.〔(Sample crops )〕 However, some samples of this lens have also been reported to exhibit deficiencies and operational problems〔(FM reviews – Canon EF 24–70 mm f/2.8L USM )〕 not present in the older 28–70 mm lens, including poor sharpness and/or chromatic aberration. According to the head of a US lens rental firm, the f/2.8 Mk I lens "definitely has some reliability issues and a lot of copy-to-copy variation, at least some of which relate to its design." Early reports on the f/2.8 Mk II indicated significant improvement in optical quality. The aforementioned rental firm head stated, All versions of the lens include sealing against dust and water, although they are not waterproof. The f/2.8 Mk I includes an 8-bladed curved diaphragm, while both the f/2.8 Mk II and f/4 include a 9-bladed curved diaphragm. The diaphragm of the f/2.8 Mk I remains nearly circular from f/2.8 to f/5.6, according to the Canon Press release from 2002. Characteristic of zoom lenses, it exhibits some barrel distortion at its shortest focal length. == Reverse zoom == An unusual aspect of the f/2.8 Mk I lens (and the 28–70mm f/2.8L) is that its barrel extends as it zooms toward its shortest focal length. When used with the supplied lens hood, which attaches to a non-moving part of the lens, this extension results in a properly matched shade at every angle of view. Most zoom lens hoods are designed for only the widest angle of view, offering progressively inadequate shade at longer focal lengths. This reverse zoom is illustrated with the following two pictures: File:Canon 24-70 mm F2.8 lens side at 24 mm.jpg|Lens at 24 mm with a UV filter File:Canon 24-70 mm F2.8 lens side at 70 mm.jpg|Lens at 70 mm with a UV filter File:CanonEF24-70mm.jpg|Lens with lens hood At the telephoto end (70 mm), the end of the lens is the most retracted providing the most shade protection from the lens hood. At the widest end (24 mm), the end of the lens is the most protruding providing the least shade protection from the lens hood. The f/2.8 Mk II lens, however, has a more conventional design, with the barrel extending as the focal length increases. The lens hood is much shorter than that of the Mk I version.〔 The f/4 lens shares the same conventional design. 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 24–70mm lens」の詳細全文を読む スポンサード リンク
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