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When using the mirror lock-up mode or Nikon’s exposure delay mode, is it true that keeping the mirror raised for some time requires more battery power? Is the mirror flipping mechanism continuously using electric power to keep the mirror up?

Please cite your sources, if possible.

I’m particularly interested in the Nikon D750. It’d be also nice to know how other DSLR brands and models operate.

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    Nikon is the only place you'd be able to get a definitive answer, but I doubt they'd say. Given that mirror lock-up requires AC or a minimum battery charge level, odds are good there is at least a bit of current being drawn. – Blrfl Sep 13 '15 at 17:52
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    Why don't you just test it out vs asking us? Seems simple to test unless I'm misunderstanding the question. – dpollitt Sep 13 '15 at 18:39
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    All sensor cleaning tutorial I read recommend to do it with a fully charged battery, but haven't provided any detailed source. – Olivier Sep 13 '15 at 20:56
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    On Pentax K-system DSLRs, holding the shutter open requires power. However, holding the mirror up does not. If you pull the battery in Live View, the shutter snaps shut but the mirror stays up. – bwDraco Sep 16 '15 at 21:03
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    This may not be the most scientific method. But try putting your camera in mirror lockup mode and then remove the battery or disconnect the power source quickly. If the mirror flips down you know that the mirror requires power to stay up. If the mirror stays up then you have your answer! – Harry Sanderson Sep 18 '15 at 20:14
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Mirrors usually flip back when not energized so that debris from mounting a new lens does not reach the sensor. They are also hold in place in some mechanical means, so when not energized, they do not shake and vibrate during transportation.

Mirrors with only one latching position (e.g. spring pulls it to a closed position) will require power to keep the mirror up against the spring.

Mirrors that have two latching positions (can lock in both up and down) will not use energy when latched but will use double the energy when moving the mirror in a shot (because the camera has to overcome the latching force two times). A sudden power down will leave such a camera with either mirror up or down.

Mirror up on Nikons do use power, as a surprise power down will show that the mirror is snapped down.

  • "Double the power" would only be valid with certain kinds of latching mechanisms... is this a guess or informed? – rackandboneman Apr 10 at 15:41

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