According to the Egami Blog, Tamron has patented the optical formula for a 100-400mm f/4.5-6.3 VC.
Description of Patent
- Patent Publication No. 2016-126295
- Published 2016.7.11
- Submitted 2015.1.8
- Focus distance 103.00 247.29 389.05
- f-number 4.51 5.81 6.53
- Field of view 11.68 4.88 3.11
- Negative positive negative
- Rear focus (Group 5)
- Anti-vibration (third group)