Reading around everywhere, some people say the D3100 flips the mirror down and up before opening the shutter again when using live-view, and other people says it doesn't (which would be preferable as it could become a substitute for the missing mirror lock-up).

Feeling experimental, I tried at home, first by looking through the viewfinder and then by going in LV without lens (I know I risk dust...) and I can totally say that sometimes it does flip the mirror and sometimes it doesn't.

I tried everything but I couldn't grasp what causes this change in behaviour.

Has anyone any idea of what may cause the D3100 to flip the mirror in LV?

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    \$\begingroup\$ The reason it flips the mirror down in live view before taking a picture is so the light meter can run for a little bit. It might not do that therefore depending on the metering mode. Try full manual verus auto metering and see if it makes a difference. \$\endgroup\$ Commented Jan 16, 2013 at 13:35
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    \$\begingroup\$ This may not be the answer you are looking for. Move along. Or may. Sony pellucid mirror cameras focus using phase detect without needing to flip the mirror to allow light to reach the phase detect system. All SLRs without a part silvered mirror need to flip the mirror to allow phase detect focusing during live view. I'd guess that this is what you are seeing. If the camera decides that it is in focus then it may decide to not flip the mirror. [It's 6am and almost bedtime. If that doesn't make sense I'm asleep]. \$\endgroup\$ Commented Jan 16, 2013 at 17:12
  • \$\begingroup\$ My tests were all without a lens mounted and thus manual exposure, manual focus, and I remember quite well to have disabled flash and auto-iso. I'll try again later with all these and a lens mounted however. \$\endgroup\$
    – Marco Mp
    Commented Jan 16, 2013 at 17:27
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    \$\begingroup\$ Mistery solved thanks to Russell - it was not exactly what you said but close. The mirror seems to drop if and only if continuous shooting is enabled, most likely to refocus between frames using phase sensors. When single shooting, it relies on contrast focus detection and thus does not drop the mirror. \$\endgroup\$
    – Marco Mp
    Commented Jan 16, 2013 at 21:12
  • \$\begingroup\$ possible duplicate of Why Live view slaps the mirror back down when you take the shot as oppossed to leaving it up and actuating shutter curtain? \$\endgroup\$
    – AJ Henderson
    Commented Dec 26, 2013 at 20:12

1 Answer 1


In my point of view it has nothing to do with focus detection capabilities since you are in manual focus mode. It more likely that in single shooting the processor can handle live view function with single shooting but for continuous shooting the live view will be taken on hold to empty the buffer, focus the processor on image processing and provide the highest fps rate possible.


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