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When looking at taking photos such as star trails where it requires a significant exposure time, is it more power efficient to use Bulb mode or taking multiple shorter exposures?

Would keeping the shutter open in Bulb mode for an hour over expose elements of the composition?

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Without actually testing, I am reluctant to say with absolute certainty, but I won't let that stop me -- I will just make a list of assumptions :-)

Assuming stacked exposures of the same total time as the single bulb exposure, that your are not using dark frame noise reduction, that sensor power efficiency does not get significantly worse as it heats up and that your camera does not violate the laws of physics, it is going to take (ever so slightly) more energy to perform multiple exposures, just because you have to move the mirror/shutter and the processor will have to work a little harder processing multiple images.

Of course there are plenty of other advantages to stacking, but I do not think power savings is one of them.

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    Thanks. Seems legit. I'm reasonably certain my camera doesn't violate the laws of physics. I haven't seen it do anything I'd consider a violation. I wish it would though, that would be really interesting. – Tim Jul 18 '13 at 3:24
  • There's other laws in work besides those that dictate the power usage of a system camera. The laws of battery drainage. There might be a small difference in it when you draw the power in one long haul instead of splitting it into a number of short stints. – Esa Paulasto Aug 17 '13 at 14:41
  • I would also point out that one needs to achieve at least a minimum signal level to make stacking effective as well. If one needs a 180 second exposure, you could achieve that by either stacking ten 18-second exposures, or say 90 two-second exposures. The stacking the two second exposures will produce a complete image, however it will lack the color fidelity and certain nuances of detail that the ten 18-second exposures bring to the table. In other words, actual SNR trumps virtual SNR (if stacking say night sky photos is the goal.) – jrista Aug 19 '13 at 2:13

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