Canon EOS Rebel T6i EF-S 18-55mm IS STM Lens Kit Instruction Manual - Page 163

Mirror Lockup to Reduce Camera ShakeK Camera vibrations caused by the mirror's reflex action is called "mirror shock". Mirror lockup can reduce the blur caused by camera vibrations. This is useful especially when you are using a super telephoto lens or shooting closeups (macro photography). Mirror lockup is enabled by setting [9: Mirror lockup] to [1: Enable] in [54: Custom Functions (C.Fn)] (p.342). 1 Focus on the subject, then press the shutter button completely.  The mirror will swing up. 2 Press the shutter button completely again.  The picture is taken and the mirror goes back down.  After taking the picture, set [9: Mirror lockup] to [0: Disable]. Shooting Tips  Using the self-timer , with mirror lockup When you press the shutter button completely, the mirror locks up. The picture will be then taken 10 sec. or 2 sec. later.  Remote control shooting Since you do not touch the camera when the picture is taken, remote control shooting together with mirror lockup can further reduce camera shake (p.350). With Remote Controller RC-6 (sold separately) set to a 2-sec. delay, press the transmit button to lock up the mirror, and the picture will be taken 2 sec. after the mirror lockup. 163