[Patent] Canon’s New EF 600mm f/4 and EF 400mm f/2.8 Lenses

600mm f/4

400mm f/2.8

Japanese site egami (Google translated) spotted two new Canon patents. The patents refer to the EF 600mm f/4 and the EF 400mm f/2.8 lenses. The lenses will have reduced size and weight. The 600mm will have 15 elements in 9 groups, the 400mm 14 elements in 9 groups (more specs below). Performance charts:

Performance Chart 600mm f/4

Performance Chart 400mm f/2.8

More specifications (machine-translated)…:

  • Patent Publication No. 2012-88427
    • 2012.5.10 Release Date
    • 2010.10.18 filing date
  • Example 1
    • Focal length f = 585.00mm
    • Fno 4.12
    • Image height 21.64mm
    • Length 468.50mm lens
    • BF 90.78mm
    • 15 sheets of 9 group lens configuration
    • One aspherical surface a
    • 2 UD glass sheet
    • One fluorite
    • A plane diffraction
  • Example 2
    • Focal length f = 391.86mm
    • Fno 2.88
    • Image height 21.64mm
    • Length 367.51mm lens
    • BF 50.01mm
    • Lens Construction 14 elements in 9 groups sheet
    • 2 2 aspherical surface
    • 1 UD glass sheet
    • One fluorite
    • A plane diffraction
  • Group 3 consists of positive and negative positive
  • Inner Focus (group 2)
  • Strengthen the refractive power of the front lens group, and to shorten the overall length, the sensitivity is increased, it is difficult to manufacture and assembly
  • The number of lens group at the end of the super-telephoto lens is determined by the balance of the total length and chromatic aberration
    • And shorten the length and reconcile, the correction of chromatic aberration, the number will increase
      • It is important to the length of each degree
    • Weight of the first lens group, 70% to 9 on the whole
      • Canon patents is reduced to three the first group
      • Aspherical and one eye in group 1 group, field curvature correction, the distortion
      • Diffractive optical element and the second two groups in the first group, the chromatic aberration correction

[egami via CR]

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