Backscatter (photography)

Cases include nighttime and underwater photography, when a bright light source and reflective unfocused particles are near the camera.

[5] The artifact can result from the backscatter or retroreflection of the light from airborne solid particles, such as dust or pollen, or liquid droplets, especially rain or mist.

[2][4] The image artifacts usually appear as either white or semi-transparent circles, though may also occur with whole or partial color spectra, purple fringing or other chromatic aberration.

[2]In underwater scenes, particles such as sand or planktonic marine life near the lens, invisible to the diver, reflect light from the flash causing the orb artifact in the image.

[10] Prominent paranormal investigators such as Joe Nickell have agreed with skeptic-debunkers' assessments that orbs result from natural phenomena like insects, dust, pollen, or water droplets.

The backscatter of the camera's flash by motes of dust causes unfocused orb-shaped photographic artifacts.
A hypothetical underwater instance with two conditions in which circular photographic artifacts are likely (A) and unlikely (B), depending on whether the aspect of particles facing the lens are directly reflect the flash, as shown. Elements are not shown to scale.
Circular unfocused visual artifacts caused by raindrops.
Dust particles reflected by a smartphone flash.
A single orb in the center of the photo, at the person's knee level