As for single frame, except that the mirror does not click back into place while the shutter-release button is fully pressed, allowing the user to control the timing of the click made by the mirror, which is also quieter than in single frame mode. In addition, a beep does not sound regardless of the setting selected for Beep in the setup menu.
QC (quiet continuous) shutter-release
While shutter-release button is held down, camera records up to 3 frames per second.
* Camera noise is reduced.