One component in the optical system of a dSLR camera is a mirror that moves when you press the shutter button. The vibration caused by the mirror movement can result in image blur when you use a very slow shutter speed, shoot with a long telephoto lens, or take extreme close-ups. To eliminate this possibility, your Canon EOS 77D camera offers mirror lockup, which delays the shutter release a little longer than normal so that the picture isn't recorded until after the mirror movement is completed.
Mirror lockup eliminates the chance that mirror movement blurs the photo.
Of course, you should also mount the camera on a tripod so that camera shake caused by handholding the camera doesn't create blur.
You can take advantage of mirror-lockup shooting only in the P, Tv, Av, or M exposure modes. Enable it through Custom Function 10, as shown here.
Mirror lockup eliminates the chance that mirror movement blurs the photo.Mirror-lockup shooting requires a special picture-taking process: Press the shutter button once to lock up the mirror, release the button, and then press it all the way down again to take the picture.
