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A new patent showing an optical formula for an EF 100-400 f/4.5-5.6 DO has made an appearance. The patent also shows what appears to be a new 70-300 f/4.5-5.6 DO optical formula. Canon appears to be continuing their investment in diffractive optics R&D, though we haven't seen a new DO lens in quite some time. I don't think we'll see a new 100-400 with the technology, and with the current 70-300L being pretty small and light, I'm not sure we'd see a new 70-300 DO either. It's good to see they continue to develop the lens concepts though, and hopefully we see some new ones in the coming years.
- Patent Publication No. 2014-89385
- Publication date 2014.5.15
- Filing date 2012.10.31
- Example 1
- Zoom ratio 3.78
- Focal length f = 103.00-200.00-388.94mm
- Fno. 4.63-5.24-5.83
- Half angle ω = 11.86-6.17-3.18 °
- Image height Y = 21.64mm
- 228.82-273.58-303.10mm total length
- BF 69.48-90.93-105.73mm
- Example 6
- Zoom ratio 4.00
- Focal length f = 72.50-135.00-289.99mm
- Fno. 4.44-5.04-5.85
- Half angle ω = 16.62-9.10-4.27 °
- Image height Y = 21.64mm
- 143.91-177.69-203.15mm total length
- BF 39.10-39.10-39.10mm
Source: [EG]
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