Zen and the Pursuit of Mirror Lock-Up

For many die-hard photographers, a camera just isn't complete unless it has a mirror lock-up mechanism. Others are thinking, "what the heck is it?"

In single-lens reflex (SLR) cameras, a mirror is used so that you can see an image of what you are photographing through the lens. When the shutter release is pressed, the mirror swings up and out of the way so that the film can be exposed. The action of the mirror swinging out of the way temporarily blocks your view of the scene until it returns to position. This motion also causes minor vibrations in the camera body.

In most cases, the vibration caused by the mirror is not significant enough to affect your photographs. However, there are situations when you might want to prevent it, mostly when using high magnification such as when using a very long focal length lens ( such as a 800mm) or when making macro photographs. In these cases, the magnification of the optics increases the apparent effect of the mirror movement.

For those who have a camera capable of it, mirror lock-up locks the mirror up and out of the way so it doesn't move during the exposure. Obviously, if the mirror is up, you can't see to compose your image, so that has to be done first. This limitation makes it necessary to limit your use of mirror lock-up to objects that don't move (or very patient people subjects!).

Many newer cameras, especially those not intended for professionals, don't come with a mirror lock-up switch. Also, I've noticed it to be missing on many plastic bodied cameras, possibly due to the fact that mirror lock-up is an all-mechanical operation and these cameras are heavily electronic. (?) In either case, if you are interested in a camera with mirror lock-up capabilities, either be prepared to spend extra for a high-end camera, or look for an older style camera from an era when this feature was more important to manufacturers (the Nikon F3 is a good example).