Gunsight, is it off or is that the dimmest setting?

[xnomad]

So according to the manual the gunsight is off and you need to turn it on. The blue reticle you see when you start, is that supposed to be the gunsight off, or is it on its dimmest settings?

Surely if it's off you wouldn't see a reticle, but I don't see any way of turning it right off so there is no reticle.

I've seen some photos of gunsights without any power going through them and there is nothing to see. I can't see how ambient light light could get into the system to project any sort of image.