Don’t get spooked by white, ghost-looking round spots that can appear in photos when taking photos inside with a flash. They are not celestial orbs as some often wonder. They are caused by dust.
Dust particles floating in the air when taking flash photos with a digital camera may be captured in pictures. Often referred to as dust halos, the particles are randomly spaced throughout an image. There may be just a couple of spots, or the problem can be so bad that you hardly see the picture.
Compact cameras are particularly prone to dust halos because the flash is so close to the lens. The light from the flash catches the dust and bounces back into the lens.
Preventing dust spots
When dust is present, there is really not much that can be done to avoid the problem. If you use an external flash, the phenomenon can be minimized or prevented.
Sometimes zooming in a bit and using a wide aperture will help. But realize that the more you zoom in when using a built-in flash, the more red-eye can be expected when photographing people.
A similar phenomenon occurs taking outside flash photos when it rains or snows.