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

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:

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]