Sigma patents 500mm f/4 lens
Sigma filed a patent in Japan for a new 500mm f/4 lens. Sigma currently has a 500mm f/4.5 EX DG APO HSM model that was announced back in 2005:
Patent details:
- Patent: 2011-70043
- Patent filing date: Sept 28, 2009
- Focal length: 489.9938
- Aperture: 4.1004
- Angle of view: 5.0498 °
- Back Focus 90.3449mm
Source
