When a security camera loses power, buyers assume the loss window equals the outage. The camera was off, so nothing was recorded, and when the power returns it picks up where it left off. The second half of that assumption is where the expensive gap lives. Between power returning and the camera being genuinely operational there is a boot sequence that routinely runs 40 to 90 seconds, and what happens inside that window determines whether an incident that occurred around the outage was captured at all.
What happens inside the boot window
The sequence is roughly: power on, storage check, network link, DHCP, time sync, authentication to any cloud service, then streaming and detection come up. On models with an SD card that was not cleanly unmounted, add a filesystem check in front of all of it. During the whole sequence there is no recording and no motion detection. An intruder who cut power at 14:00:00 and left at 14:01:30 may be fully inside the blind window even though power was restored within a minute.
Cheap cameras boot fast and badly, skipping the storage check and mounting a damaged filesystem, which trades a shorter gap for corrupted recordings discovered weeks later. The honest spec to compare is time from power applied to first recorded frame after a dirty power loss, and most listings do not publish it.
Pre-roll lives in RAM, and RAM forgets
The few seconds of video before a motion event, the feature that shows what led up to the trigger, is buffered in memory and written when the event completes. Pre-roll is exactly the footage around the moment of the outage, and it is exactly the footage that does not survive a power cut. Whatever happened in the seconds before the power was cut is unrecoverable on virtually every consumer camera, no matter how good the post-event recording is.
Timestamps are the second casualty
Cameras have no battery-backed clock worth the name on most models. After an outage, until NTP succeeds, a camera either holds its clock or resets toward an epoch date. Recordings from that camera then carry timestamps that are wrong by minutes, hours or decades. Two cameras covering the same entrance that rebooted at different times can disagree about when the same event happened, and a timestamp disagreement is exactly what turns usable footage into inadmissible footage in an insurance or police context.
- Models with an RTC backup chip hold time through outages of days.
- Models without it depend entirely on NTP reaching the device.
- The failure is silent: the video looks perfect, the timecode is fiction.
A buying question worth asking: after a power loss, does the camera hold time until the network returns, or does it stamp recordings with whatever it believes?
Detection does not queue
Motion during the outage and the boot window is not stored for later analysis. It simply never happened, as far as the camera is concerned. Cloud events that fired just before the outage may push late or never, because the event pipeline was interrupted. Local SD recording resumes once the camera is up, which is why an SD slot matters even on cloud-first cameras: the outage recovery path runs entirely locally.
What a UPS actually buys, and what it does not
A small UPS on the camera keeps the camera alive through short outages and, more importantly, makes every power event a clean shutdown instead of a dirty one. A UPS on the camera alone is only half a solution: a camera that stayed up while the router lost power still cannot reach the cloud or your phone, and may not even hold its NTP time. The pair that matters is camera power and network equipment power. Also worth stating plainly: most outages in a home are not the grid. They are breakers switched off for garden work, cleaning, renovations, and a vacuum cleaner on the wrong socket. Those are precisely the events nobody schedules recording around.
What to ask before you buy
- Time from power restored to first recorded frame, measured after an unclean shutdown.
- Whether the camera holds time through an outage (RTC) or waits for NTP.
- What the SD filesystem does after dirty power loss: check-and-recover, or mount-and-hope.
- Whether events recorded locally during a cloud outage sync back afterward.
- Whether the camera distinguishes power loss from tampering and notifies either way.
The gap after an outage is the only part of a camera's coverage that no firmware update has ever fixed, because it is bounded by physics: storage checks, network handshakes and time sync take time. What separates good designs from bad ones is whether the vendor measured the window, published it, and kept it short.
The surveillance camera collection includes models with RTC backup and fast recovery paths, and the CCTV camera manufacturer page documents recovery behavior per platform. The wider range sits on XingLiao, and boot-time and timestamp questions can be sent through the contact page.
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