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Canon Files Patents for 45mm, 50mm, 60mm Prime Lenses

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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.

canon-lens-patent

canon-lens-patent-01

Patent description (machine translated):

  • Patent Publication No. 2013-57802
    • 2013.3.28 Release Date
    • 2011.9.8 filing date
  • Example
    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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