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In burst mode, when a camera is writing a burst of images to its SD card, can it be writing multiple images simultaneously or does it still do them one at a time?

I know it’s possible to get data corruption if you accidentally turn a camera off while it’s still writing a burst of images to the card. But if it writes them one at a time, it should only be possible to get ONE single corrupted image from that, right? The one that was being written at the moment the power was cut off. Because the ones before that were completely written, and the ones after that will be completely missing. Is that right?

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  • \$\begingroup\$ My camera (Sony A6000) ran out of battery while taking a long bulb exposure (30 minutes). Much to my surprise, the image was still written to storage. \$\endgroup\$
    – gerrit
    Commented Nov 8 at 7:18
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    \$\begingroup\$ @gerrit That's because most cameras don't wait until the battery actually dies. They start shutting down when the battery gets to a preset level, such as 5%. This gives them enough time to save what needs to be saved before shutting themselves off. \$\endgroup\$
    – Michael C
    Commented Nov 8 at 18:43
  • \$\begingroup\$ @MichaelC concur - I have a gopro max, and when using a brand-new knockoff battery, the voltage would "fall off a cliff" and it would produce playable video but without any stabilisation, on the file being recorded PLUS the previous file, which was up to 8 minutes old. Authentic batteries must have warned the camera "Immabout to die" and avoided broken video. \$\endgroup\$
    – Criggie
    Commented Nov 10 at 21:33

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I think, that what you asking is heavily depending on the implementation of the specific camera. All modern mirrorless cameras that I know (and probably most somewhat modern cameras) do not cut the power the moment you throw the switch.

Some even do a sensor cleaning, close the shutter etc then - so whether the engineers decided to do a hard stop to operations or not, is simply their design decision.

I would guess that most cameras would try to write out the buffer before turning off that sub-system. This might exclude very simple, old or cheap cameras.

Your assumption that the buffer is written sequentially is correct. So if the camera turns off file operations in mid-write, in best case you have one single corrupted image, in worst case a corrupted SD card, as the filesystem also needs updates written to it. This could be the case if you disconnect the battery in mid-operation (if the camera does not have a capacitor to counter even that).

A word of warning: At least I have non-recoverably killed SD cards during experimentations with raspberry pie computers - but that is not comparing apples to apples, as there I actually can cut the power mid-operation.

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    \$\begingroup\$ Not only mirrorless, INHO most of mid and high range DSLRs do the same. Mu 5D Mark III "delay" the actual power off up to 10 seconds. \$\endgroup\$
    – Romeo Ninov
    Commented Nov 7 at 15:32
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    \$\begingroup\$ @RomeoNinov However, if you open the battery door while it's still writing... \$\endgroup\$
    – Michael C
    Commented Nov 7 at 22:59
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    \$\begingroup\$ @MichaelC, if .. (many stupid actions) ... :) \$\endgroup\$
    – Romeo Ninov
    Commented Nov 8 at 6:19
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    \$\begingroup\$ @Glaucoides I wouldn't trust it but even on my old PowerShot it appears to successfully write even if you press the power button immediately after shooting. That's no surprise. Whether a rotary switch (as on my EOSs) or a button (as on my PowerShot) the power switch is an input to the CPU in the camera, much like the power button on PCs from the last 30 years \$\endgroup\$
    – Chris H
    Commented Nov 8 at 8:50
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    \$\begingroup\$ @RomeoNinov Never underestimate the power of human stupidity. Einstein is reputed to have said, "Two things are infinite: the universe and human stupidity; and I'm not sure about the universe." \$\endgroup\$
    – Michael C
    Commented Nov 8 at 18:49
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The power switch does not instantly cut the power, as with a room light.

It's more like when you turn off a PC (not at the wall) – it completes outstanding tasks, and for one thing, on a compact camera, the system has to retract the lens.

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  • \$\begingroup\$ However, if you open the battery door while it's still writing... \$\endgroup\$
    – Michael C
    Commented Nov 7 at 22:58
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    \$\begingroup\$ @MichaelC or drop it in to a fire. Or it's crushed by an elephant. \$\endgroup\$
    – Weather Vane
    Commented Nov 7 at 23:32
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    \$\begingroup\$ @WeatherVane You finally see incontrovertible proof of flying saucers, and reach for your camera to shoot off a long burst of images. Due to the shock of seeing such an event, you drop your camera in mid burst, where it lands on a sharp rock, pops the battery door open and releases the battery. Aside from the flying saucer this is a real potential reason for the battery being removed when it is not flat - it's just that you are not choosing to remove the battery at that time. \$\endgroup\$
    – Peter M
    Commented Nov 8 at 19:18
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    \$\begingroup\$ @WeatherVane This question isn't about opening the back of film cameras, but this conversation is about the critical thinking ability of newbies to photography, whether digital or film. \$\endgroup\$
    – Michael C
    Commented Nov 9 at 11:37
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    \$\begingroup\$ To borrow from the second analogy in your answer: When my Brother-in-Law was the IT help desk for a large company you wouldn't believe how many times an employee would shut their computer down by turning off the power bar into which it was plugged and then call him the next morning because their work from the end of the previous day was not saved... \$\endgroup\$
    – Michael C
    Commented Nov 9 at 11:41
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If you remove the battery or the battery runs out completely you'll get real damage and potentially kill the SD card in a single go (unlikely but it happened), but the switch you flip does not do that, it just tells the camera what you want to do, and the camera will decide on its own how to handle that.

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