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Friday, May 17, 2013

Canon Patents - 500mm f/4, f/5.6 ; 600mm f/4 ; 800mm f/5.6

The Japanese photography blog, Egami has uncovered more Canon patents. This time they involve a 500mm f/4 and f/5.6 lens plus a 600mm f/4 and 800mm f/5.6 Diffractive Optics (DO) lens design. The patents seem to suggest an emphasis on weight reduction by rearranging the lens group inside the barrel. I have the Canon 400mm f/4 DO IS lens and it is one of my favorite lenses for wildlife photography. You can read the original article by visiting Egami's website.

Canon files thousands of patents a year. Many do not end up in a marketable product. They are the results of a massive research and development effort. The patents protect Canon's intellectual properties and prevent competitors from utilizing the same technology.

Patent Publication No. 2013-92575 

  • Publication date 2013.5.16
  • Filing date 2011.10.24

How to reduce the size of the large-aperture super telephoto lens (translated)

  • Effective diameter of the first group with the largest
  • I reduce the number of the first group
  • It is necessary to reduce aberration by increasing the number
  • Can not reduce the aberration and reduce the number
  • I increase a refractive power of the first group
  • The thickness of the lens increases, the effect of weight reduction is canceled
  • Impact of manufacturing error is large high refractive index

Canon Patent

  • The aspherical in the first group
  • Performing a variance of sensitivity was composed of opposite sign component of the first group, and also, prevent an increase in thickness
  • DOE is provided to correct chromatic aberration with a small number of lenses
  • Inner focus
  • Anti-shake

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