Objects in back of the camera can be reflected in the glass and look very much like a ghost. If you have to shoot through glass, place the lenses flush with the pane. Doing this makes the glass simply another lenses and will cut down on reflections. Finally, you always have to check where your light sources are. Try to avoid shooting toward a bright light, such as the sun, moon, or stark artificial lights.
Lenses flare is when the light reflects back and forth between the lenses in the camera.
A way to spot this problem on a negative it to see if you can see the light source in the frame, and check and see if the orbs are arranged in a straight line away from it. If they are, you probably have lenses flare. On the subject of orbs, there is another problem that can cause them. If there is dust or moisture on, or in, the camera or the lenses the result can resemble them. Looking at the frames on either side of the one with the orb can clear this up.