The rear command dial is used as described below.
Rotate :Highlight menu items, choose the desired combination of shutter and aperture (program shift), choose a shutter speed, adjust settings in the quick menu, choose the size of the focus frame, or zoom in or out in full-frame or thumbnail playback.
Press :Zoom in on the selected focus area or (in playback mode) the active focus point. Press and hold to choose the manual focus mode focus display.
Formatting Memory Cards
The format menu can also be displayed by pressing the center of the rear command dial while pressing and holding the 
button.
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