Canon 16-35 f/2.8 DO Patent

Canon 16-35 f/2.8 DO Patent

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This is an interesting DO patent from Canon. There seems to be a lot of them showing up, but no new DO products in a long while.

I’ve been told the lack of an A+ filterable wide angle from Canon for a full frame camera will be addressed sooner than later. Yes, there’s Zeiss, but most want AF.

Patent Publication No. 2011-145518

  • Release Date 2011.7.28
  • Filing date 2010.1.15

Example 1

  • Focal length f = 16.48 – 24.00 – 33.95 mm
  • Fno = 2.91
  • Half angle of 52.70 – 42.04 – 32.51 °
  • 4 aspherical surfaces
  • Zoom Ratio 2.06
  • Four-group zoom lens plus a negative sign
  • Second lens focusing is performed by Inner Focus
  • Solve various problems using the diffractive optical element
  • The astigmatism of the telephoto kept in order, to increase the refractive index of the positive lens
  • A high refractive index, chromatic aberration occurs
  • Aberration and astigmatism in the center of the telephoto image has a correlation, it is difficult to simultaneously correct
  • Made achromatic diffractive optical element, a positive lens astigmatism correcting high refractive index

Source [EG]

cr

 

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