Why does some DSLR live view mode drop the mirror before taking the photo?

Asked 12/26/2013

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2 answers

On a DSLR, live view keeps the mirror up so the sensor can provide the preview. When I press the shutter, though, some cameras briefly drop the mirror and then raise it again before the exposure. Why is that necessary instead of just firing the shutter with the mirror already up?

live-view autofocus dslr metering mirror

Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0

Photography Stack Exchange contributor

12y ago

2 Answers

Two possibilities, focusing and metering.

Often when shooting in live view, the mirror snaps down to use the phase detect auto-focus, then snaps back up to take the image and remains up to keep live view going. If your camera supports using only contrast based auto-focus, then you can avoid that cycle.

Similarly, it may want to use the light metering capabilities that are available when the mirror is down, depending on how well the sensor can meter for itself as well.

In either case, it is often a setting that can be adjusted in the menus. I know my 5D Mark iii has a setting that will allow the photo to be taken directly in LiveView without the mirror flipping down.

Originally by user11392. Source · Licensed CC BY-SA 4.0

user11392

12y ago

AI Answer

Generated from our catalog & community — verify before relying on it.

On some DSLRs, the mirror drops briefly in live view mainly for camera operation, not because the exposure itself requires it.

Common reasons mentioned are:

metering: some cameras use their normal metering system with the mirror down for a final exposure reading
autofocus: some models briefly drop the mirror to use phase-detect AF instead of live-view contrast AF
mechanical design limits: on certain entry-level models, the mirror and shutter are linked by a simpler shared mechanism, so the camera must cycle them in a fixed sequence

More advanced bodies may be able to take the shot directly in live view without that extra mirror movement, and some cameras offer menu options that change live-view AF/shutter behavior.

So the short answer is: it depends on the camera design and settings. If your DSLR drops the mirror in live view, it is usually because it needs either its standard metering/AF system or because its shutter-mirror mechanism is not designed to fire independently while staying in live view.

Why does some DSLR live view mode drop the mirror before taking the photo?

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