Canon filed patent to increase dynamic range by using a Neutral Density (ND) filter on half of the measured field. This is a pretty complex one and I am not 100% sure I got it right (any help welcome).
The described system works by getting different degrees of light intensity from the Dual Pixel auto-focus (DPAF) points (i.e. split pixels) on the sensor. The patent says the ND filter is placed on 50% of the measured field: different amounts of light hit the split AF pixels needed for DPAF (this means both of the split pixels are used to measure the DR). The result is an output that’s able to render an increased dynamic range to the sensor, and a easier to measure differential signal from the DPAF points. It is not as easy as I am trying to put it :-) To learn more about Canon’s Dual Pixel Auto-Focus technology have a look here.
- Patent Publication No. 2015-87401
- Published 2015.5.7
- Filing date 2013.10.28
- Canon patents
- Dual Pixel AF
- And set up a half-ND filter at the pupil position of the lens
- Half ND filter can be switched