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

[Cap'n Crunch]

Some reflector sights will cast an image with the bulb off, it all depends on the make, but have seen images on unpowered units.

http://www.youtube.com/watch?v=YgLVB0Ghmb0&NR=1

Here's a clip of an unpowered Japanese reflector, you can see there is no bulb lit when he puts the camera above the sight looking into the projector lens. And the reticule reflection image is bluish.