Tech Check Mirror lock-up
How to avoid your DSLR’s design creating vibrations that spoil your image sharpness
What is mirror lock-up?
Every DSLR has a mirror that enables you to look into the viewfinder and out through the lens. The mirror flips up when you take a photo and flips down just after; it’s the ‘clunking’ noise when the shutter button is pressed. It has to do this to get out of the way of the light during the time the exposure is being made. But this movement can cause vibrations within the camera body.
Why would that matter?
For a lot of shooting situations, it doesn’t matter. If you’ve set a fast
shutter speed, those vibrations won’t have any effect on image quality; but if you are using exposures from about 1/8 sec and slower, the slap of the mirror and the resulting vibrations could cause an issue, especially when you’re shooting at the extremes of focal length, for example when using a macro or a telephoto lens.
Even though your camera will have some kind of internal dampener to reduce mirror slap vibrations, using your DSLR’s mirror lock-up facility means that you can remove any chance
of a slight wobble affecting the sharpness of your photograph.
How does it work?
Once you’ve enabled mirror lockup through your menu or via your function dial, press once to raise the mirror, delay a moment and then press again to take the photo itself. The delay gives enough time for any vibrations to subside. If you’re using slow shutter speeds, you may need a tripod and possibly also a cable release to fire the shutter.