I really should have read the User Guide BEFORE taking a photo walk today.
Dual Pixel Auto Focus (DPAF) is your friend and a necessity for improved photography.
Dual Pixel Autofocus: What is it and what cameras have it? – Improve Photography
On these new Canon CMOS imaging sensors, each pixel has two photo diodes which can operate separately or together. Each diode has a separate lens over it.
When light goes through those lenses and hits the diodes, the processor analyzes each diode’s signal for focus and, once focus is achieved, the signals are then combined to record the image.
Each pixel on the sensor, then, has a dual role.
That dual role is what makes DPAF sensors different.
In other kinds of imaging sensors, some of the pixels are used for focus and the rest record the image, but none does both.
In Canon imaging sensors, 80% of the pixels (horizontally and vertically) play that dual role.
The sensor on the EOS 5D Mark IV, for instance, is 6720 x 4480 pixels. At 80% coverage (5376 x 3584) more than 19 million pixels have DPAF.
By comparison, the Sony a7R iii sensor is 7952 x 5304 pixels and has 399 phase detection auto focus points.
While mirrorless cameras have been using phase detection auto focus in imaging sensors for some time, DSLRs typically use a separate phase detection auto focus sensor for focusing while the mirror is down and the viewfinder in use, and switch to contrast detection auto focus on the actual imaging sensor when the mirror is up and you’re using Live View or recording a video.