Here's What Canon's DualPixel AF Can Do For You
Not only can dividing pixel boost autofocus sensitivity, but also dynamic range.
When it comes to technology development, I love happy accidents. The features that appear, not because they were designed in, but because they just so happened to be a bonus. Apollo Flight Director Gene Kranz would say he didn't care what something was designed to do, but what it CAN do. And thanks to another patent application this week, we've come to learn a bonus to Canon's Dual Pixel AutoFocus ... and that's the potential for increased dynamic range.
Discussing the technology behind dual Pixel AF, the Canon Patent Application to the Japanese Patent Office (number 2019-129491) outlines how dual pixel autofocus works by splitting a pixel into two separate halves, called "photo diodes." Each diode is then amplified at different levels to determine its phase detection. The result is highly accurate autofocus on the subject, covering over 80% of the images sensor. You can read more about how Canon accomplishes this here.
But engineers have clearly been experimenting with what else the photo diodes can measure and how amplifying them can achieve increased dynamic range. The result is what CanonWatch watch refers to as a kind of "dual ISO," where the diodes are exposed at different ISO settings simultaneously. The image is then processed in real-time at the pixel diode level.
Now, this doesn't mean that we'll see what I'm going to call "dual pixel ISO" in the next generation DSLRs or mirrorless designs. In fact, buried deep within the patent application there's a sketch for how dual pixel autofocus may be used for a radar sensor in a car. But if Canon is planning on using this technology in a future camera, it sounds like it'll be pretty cool.
You can check out other Canon patents here.