What makes the Canon 7D different from all the other cameras is the software. Canon had to regain it’s mojo after having it’s ass whipped by Nikon. They did it by spending “muchos dinaros” in software development. One of them is the new autofocus system.
So how may autofocus modes is there? The are only 2 modes:
- One Shot AF. It’s for static subjects. The 7D will focus and lock the focus for as long as you keep the focus button pressed1. You can then move the camera and reframe.
If you have removed the focus from the ½ press of the shutter, you don’t have to keep your finger on the “focus button.”
- AI Servo AF. It’s for moving subjects. The 7D will keep on focusing as long as the focus button is pressed. The Canon 7D will continue to update the focus.
The problem is: How do you press the shutter and release it back only to the ½ pressed position so the 7D can continue focusing? I can’t. That’s one of the reason why I prefer to remove the focus from the shutter button. I can keep pressing the focus with my thumb on the AF-ON button.
- AI Focus. It’s for switching automatically from the One Shot AF to the AI Servo if the 7D senses that the subject is moving.
Either the ½ press of the shutter or the AF-ON or what you have defined to be the focus button in your custom functions ↩