Explanation: While taking photos and using manual focus point selection this button will select the focus point in the center. You can change the behavior of this button in the custom setting menu f2 OK Button (shooting mode).
While watching images on the camera monitor the OK button will take you
- from viewing an enlarged part of an image back to the display of the full image
- from the display of a full image to the retouch menu.
And if the displayed image is the first frame of a movie the OK button will start the movie playback.
In camera menus pushing the OK button will confirm the choice of a menu option.
In the live view mode and focus setting AF-F for tracking of moving subject the OK button will actually start focusing and subject tracking.