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Patent Time
A patent showing a new teleconverter has made an appearance. It appears to be a 2.7 or 2.8x TC. What effect woud it have on aperture? A 400 f/2.8L IS II would become 1120mm at f/8. All well and good, but the missing f/8 autofocus on the 1D X makes this one a bit strange with the current line of camera bodies.
Patent Publication No. 2012-47869
- 2012.3.8 Release Date
- 2010.8.25 filing date
Example 1
- -83.98mm focal length
- Expansion rate β = 1.996
- Lens Construction 5 group nine
Example 3
- -41.91mm focal length
- Expansion rate β = 2.779
- Lens Construction 5 group nine
Canon's patent
- Rear converter is to increase the focal length, F number, the residual aberration
- When doubled, twice the lateral aberration, longitudinal aberration is 4 times greater rate of expansion, because the F-number is also double, longitudinal aberration is twice per depth of focus
- Rear converter configuration consisting of three groups of positive and negative positive
- Reduce the aberration of the rear converter itself
Source: [EG]
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