Canon filed a new patent in Japan. The new patent describes the increase dynamic range by using a Neutral Density (ND) filter on half of the measured field.
Introducing a neutral density filter for only half the field, you get differing amounts of light to AF pixels that are split on the same axis as the filter. This would increase the differential output of the sub-pixel pair as you pass through sharp focus.
According to the patent the camera the upcoming Dual-pixel AF CMOS sensor will carry built-in ND filter. See details below.
Canon patent to increase dynamic range with use of Neutral Density filter (using Dual Pixel AF)
Patent Publication No. 2015-87401 (Google Translated)
- Published 2015.5.7
- Filing date 2013.10.28
- Dual Pixel AF
- And set up a half-ND filter at the pupil position of the lens
- Half ND filter can be switched