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Canon Files Patent For New Primes (45mm, 50mm, 60mm)

50mm f/1.4

50mm f/1.2

Egami spotted another patent filed by Canon. The patent refers to s 50 mm F1.4 , 50 mm F1.2 , 45mm F1.6 and 60 mm F1.8 lenses, and describes an apochromatic design that aims to reduce chromatic aberration.

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
[via egami]
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