The EF 400mm f/4 DO IS USM lens was announced in 2000. That is a long time we haven’t see the updates on this lens, today Canon published a new patent on EF 400mm f/4 DO IS II USM lens. See the detail below:
Interpretation and self-description of the patent literature
- Patent Publication No. 2013-64858
- 2013.4.11 Release Date
- Filing date 2011.9.16
Example 1
- Focal length f = 392.12mm
- Fno. 4.12
- Half angle of ω = 3.16 °
- Image height Y = 21.64mm
- 262.14mm length lens
- BF 69.97mm
- Two fluorite
- Materials and anomalous partial dispersion DOE to use, reduce the chromatic aberration
- Refractive power of the diffractive surface
- Strong, but can reduce the chromatic aberration of the element itself, flare increases
- The weaker, other optical element DOE play a role
- Refractive optical unit
- DOE anomalous partial dispersion and bonding materials
- DOE aspherical surface on the opposite side of the
- Vibration control
- Inner Focus
via: EG