What is mirror lockup?
Nearly all SLRs use a flip-up mirror mechanism. When you take a photo the mirror flips up out of the way to expose the film or digital image sensor. Unfortunately this mirror motion induces slight vibrations in the camera, which can result in slight blurring appearing in the photo, particularly with extremely long telephoto lenses. Cameras contain foam bumpers to reduce this mirror slap, but some vibration is inevitable in a moving reflex mirror camera. The simple solution to avoid blur caused by mirror slap is to flip up the mirror, wait at least a second or two to let the vibrations die down and then take the photo. There are two basic ways that cameras can do this. Some cameras offer true mirror lockup. Such cameras let you flip up the mirror whenever you like. They may be purely mechanical mirror lock mechanisms or they may be electro-mechanical. Most of Canon s high-end cameras offer true mirror lockup. Other cameras offer what s often known as mirror pre-fire. These cameras flip
