A useful aspect of Lockdown mode (on top of it potentially being quick) is that you can still get into the camera without unlocking it (for me it’s a double tap on the power). When you’re locked down they can’t navigate to your photos, but you might want to be able to record things.
There’s also ‘lockdown mode’ which forces a pin and hides most info from the lockscreen.
Long-press power, then select ‘lockdown’. (you may have to enable this feature in settings)
A useful aspect of Lockdown mode (on top of it potentially being quick) is that you can still get into the camera without unlocking it (for me it’s a double tap on the power). When you’re locked down they can’t navigate to your photos, but you might want to be able to record things.