Canon patent for EF 28-70mm F2.8 USM lens

By PR admin | Published: August 11, 2010

Not sure why Canon filed that patent two years ago, since the old Canon EF 28-70mm f/2.8 L USM lens was replaced by the EF 24-70mm f/2.8L USM.

Canon EF28 70mm F2 Canon patent for EF 28 70mm F2.8 USM lens

The details:

  • Patent Publication No. 2010-145831
    • published 2010/07/01
    • filled 2008/12/19
  • Embodiment 3
    • focus distance f=28.7-68.00mm
    • Fno=2.92
    • angle of view 74.02-35.30
    • image circle 43.28mm
    • lens length 177.91-168.98mm
    • back focus 46.71-75.33mm
  • Zooming, there are few changes of distortion
  • Retrofocus optical in wide angle
  • Tele-photo optical in tele-photo
    • short full length
  • Distortion is big in wide angle
    • astigmatism turns worse if it use the aspherical where the quantity is big
    • problem solving by a certain a lens was arranged in symmetry, and denying the distortion
  • Use aspherical
    • improve distortion
    • Because it is not necessary to make non-spherical surface quantity big, the astigmatism does not turn worse

Related posts:

  1. Canon files a patent for a new 24-70mm F2.8L II USM lens
  2. Canon files a patent for a 600mm f/5.6 lens
  3. Canon EF-S 15-105mm f/3.5-5.6 IS USM lens patent
  4. Pentax files a patent for a DA 12-35mm f/3.5-4.5 AL WR SDM lens
  5. Olympus 6-24mm f/1.8-3.8 lens patent

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One Comment

  1. EW
    Posted August 11, 2010 at 11:18 am | Permalink

    Patents show typical embodiments, but are not tied to a particular focal length. If the focal length were to be something new like 20-85mm, they would not want that disclosed to the competition, so would pick a different focal length for a example.

    20-85mm, by the way, is just a number I picked, and not something real.