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Comment by nullify88 | Hacker News Reader

I don't think you understand the comment parent made. Windows 10 comes with a feature called Fast Boot and it is usually enabled by default depending on RAM, driver support etc. What used to be a "proper shutdown" is now a hybrid hybernate. Parts of the OS in particular related to bootup are stored in a hybernation file which is loaded at boot time resulting in faster boots. This is because Windows can now skip driver init and load state from previous boots.

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I believe that cameras do that to the extreme (at least my now comically outdated G1 does that, I think): do a full reboot + hibernate on shutdown, which can take multiple seconds but which is fine because it's happening at a time when nobody is waiting for it, to then "boot up" in a fraction of a second because the system image is so small.

This is now my mental model for tricks like fast boot (which are obviously not applied to the full stack)

Honestly I've never noticed a difference on any of my Nikon DSLRs between waking up from stand-by and switching it off. (And I even had a D1 at some point!)

It's just instantly on and working. I also never noticed a difference in battery life, so I only used the on-off switch as a sort of button lock. I suspect that for Nikons that's really all it does, keep the camera from waking up from a button press.

I'd guess these use some fairly small, low power RAM that's for the "control plane", which is simply always on because power consumption is negligible, while the "data plane" is just a "dumb" ASIC with some DRAM which can turn on in a fraction of a second.

My Pana has noticeable shutdown lag (about 1.5s) suspiciously contrasting the immediate bootup/wake-up. I'd never have started suspecting that they do that hibernate trick if the shutdown started with screen-off instead of proudly (?) displaying a branded placeholder screen. Makes me wonder if maybe far more embedded systems that we know actually do have a slow boot process, but hide it in a slow shutdown that they run invisibly after screen off. If you are as curious as me, take one of your Nikon and flick the power-switch off-on quickly, that should show how deep it really went into off-ness.

If I hold the shutter down and flick the power switch on, it immediately takes a picture, if I flick back and forth it keeps taking pictures. There seems to be something like a 0.2 s delay between the click of the power switch and the clack of the shutter. That's more than the normal shutter lag (around ~50 ms for most DSLRs), but not much. If I do it two-handed I get around 2 fps out of the camera.

The Z6 mirrorless which I also have is noticeably slower. I'd say around ~1.5 seconds from the power switch to the shutter. From the noises it makes I'm guessing it is doing something with the IBIS in that extra time, which the DSLR does not have.

Power-up (remove battery, move power switch to "on" position, insert battery, observe time until meter (DSLR) or EVF (mirrorless) turns on) takes both of these around 1.5-2 seconds.

Edit: Old film Nikons also had pretty clever "power management". For example, on the Nikon FE the meter circuit is switched on and off automatically with the advance lever: If the advance lever is flush with the body, the cameras is off and the shutter is locked. Moving it to the shooting position (where it sticks about a centimeter out) the meter is powered and the shutter is unlocked. Even while advancing the film the meter is powered off. Very clever. Batteries last forever in it.

I don't know why, but I enjoy this little round of remote reverse engineering, thanks for playing along. "Cycling with shutter button pressed" is a very interesting technique, particularly when pointing at some digital stopwatch as timecode or something like that.

Another interesting specimen is the tiny RX0 I use for quick snapshots on the go, it seems to light up "services" to the screen in almost random visible order, with noticeable differences between a "doubleclick" restart and starting from settled state (e.g. screen lights up much later in the sequence on quick turnaround)

Indeed, I was referring to Fast Boot but did not recall the exact name. Thank you for providing further insight on how it works.

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