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Saturday, March 30, 2013

Canon Patents 45mm, 50mm, 60mm Prime Lens

Canon new patent 50mm f/1.4 lens

Egami, the Japanese Photography Blog has identified more patents filed by Canon, Japan. The patents refer to a number of lens designs : 50 mm f/1.4, 50 mm f/1.2, 45mm f/1.6, 60mm f/1.8, and describe an apochromatic design that aims to reduce chromatic aberration. You can read the original article in Japanese here.

I expect Canon to release a new EF 50mm f/1.4 II lens some time in the not so distant future because the current model's design is over 10 years old and can take advantage of the newer coatings and material technologies found in some prime lenses today.  It is important to point out that Canon ranks in the top five of patent filings and most patents do not end up in a product that comes to market but rather it is a strategy for the company to stake their claim and deny their competitors from taking advantage of the new design or technology.

Patent description (machine translated) :

Patent Publication No. 2013-57802

  • 2013.3.28 Release Date
  • 2011.9.8 filing date

Example  Focal length        Fno.    Angle of view       Focus
One         51.7                 1.45                45.4             Floating rear focusing +
Two   51.7                  1.45               45.4              Fed whole
Three 51.7                  1.25               45.4              Floating rear focusing +
Four        51.7                 1.25                45.4              Fed whole
Five       45.0                  1.6                 51.4              Fed whole
Six          60.0                 1.85                39.7              Fed whole

In many large-diameter Gaussian secondary spectrum of axial chromatic aberration

  • This problem occurs when using glass and others with the same Abbe number, a lens that is different partial dispersion ratio
  • When used in a positive lens lanthanum flint glass small partial dispersion ratio
  • When used in a negative lens of flint glass titanium large partial dispersion ratio

Canon patent

  • Using a lens with a partial dispersion ratio appropriate correcting the axial chromatic aberration secondary spectrum
  • The concave lens surface adjacent to the aperture, coma aberration correction, the sagittal flare

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