@Project wrote:
I may be totally wrong and maybe it’s a gimmick from canon but there is a Servo AF function in video mode that I can turn on or off. If it’s turned on, I can touch the screen on the subject I want to track and it will put a little white box on the subject and follow it around the screen as long as it’s within the field of view.
Yup. My M3 does the same thing. It probably works just like your T6i does in both Live View and Movie Mode. The "tracking" leans a little toward the gimmick side, though. As long as what you're tracking is the closest thing to the camera, it mostly works, albeit slowly.
Try this. Switch to Live View, and keep the camera stil.. Use AI Servo focusing.. If you can still Touch AF, then do it, and keep the subject still. Now half press the shutter, and the camera locks focus. How could you tell it locked focus? The box changed color.
When you touch AF, the white box appears on the subject, and stays on the subject as the subject moves around the screen. Now try half pressing the shutter as the subject moves around the screen. The focus box stays on the subject. What happens when the subject suddenly stops moving? The camera locks focus, right? How could you tell it locked focus? The box changed color.
In both tests, the focus did not lock until the subject was still. The camera is not maintaining focus as it tracks a subject. The focus lags behind the tracking. The subject must come to a near stop for the AF to get a lock.
Now, if you try that same test on a camera body equipped with a Dual Pixel AF sensor, the camera maintains near perfect focus while the subject is moving. It does not have to wait for the subject to stop moving before it can get an accurate focus lock. Half pressing the shutter maintains a focus lock at all times.
THAT is the performance difference between CMOS AF III sensors and Dual Pixel AF sensors.
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