The term orb describes unexpected, typically circular artifacts that occur in flash photography — sometimes with trails indicating motion — especially common with modern compact and ultra-compact digital cameras.

Orbs are also sometimes called backscatter

Backscatter

In physics, backscatter is the reflection of waves, particles, or signals back to the direction they came from. It is a diffuse reflection due to scattering, as opposed to specular reflection like a mirror...

, orb backscatter, or near-camera reflection.

Cause

Orb artifacts are captured during low-light instances where the camera's flash is used, such as at night or underwater – or where a bright light source is near the camera.

The artifacts are especially common with compact or ultra-compact cameras, where the short distance between the lens and the built-in flash decreases the angle of light reflection

Reflection (physics)

Reflection is the change in direction of a wavefront at an interface between two differentmedia so that the wavefront returns into the medium from which it originated. Common examples include the reflection of light, sound and water waves...

 to the lens, directly illuminating the aspect of the particles facing the lens and increasing the camera's ability to capture the light reflected off normally sub-visible particles.

The orb artifact can result from retroreflection of light off solid particles (e.g., dust, pollen), liquid particles (water droplets, especially rain) or other foreign material within the camera lens.

The image artifacts usually appear as either white or semi-transparent circles, though may also occur with whole or partial color spectrums, purple fringing

Purple fringing

In photography, and particularly in digital photography, purple fringing is the term for an out-of-focus purple or magenta "ghost" image on a photograph...

 or other chromatic aberration

Chromatic aberration

In optics, chromatic aberration is a type of distortion in which there is a failure of a lens to focus all colors to the same convergence point. It occurs because lenses have a different refractive index for different wavelengths of light...

. With rain droplets, an image may capture light passing through the droplet creating a small rainbow effect.

In underwater conditions, particles such as sand or small sea life close to the lens, invisible to the diver, reflect light from the flash causing the orb artifact in the image. A strobe flash, which distances the flash from the lens, eliminates the artifacts.

Below are two diagrams of a hypothetical underwater instance. In Diagram A, the faces of particles directly aligned with the camera's lens are illuminated by the flash, and thus the camera will more likely record orbs. In Diagram B, the faces of particles illuminated by the flash do not face the lens and therefore remain un-recorded.

Paranormal interpretation

Orb backscatter has been broadly interpreted as a highly variable range of paranormal phenomenon without verifiable causation — including invisible spirits, auras, angels, ghosts, energy fields, psycho-energetic artifacts, energy balls, etc.

External links

• The science of orb photos: a mathematical framework for orbs/backscatter, using holography theory.
• The science behind orb/backscatter.
• The Orb Video Archive.
• How to take photos with orbs/backscatter.
• How to avoid orbs/backscatter in underwater photos with orbs.
• Orbs: The Ghost in the Camera: Are orbs really ghosts, or a common artifact of photography? Brian Dunning
  Brian Dunning (skeptic)
  Brian Dunning is the host and producer of Skeptoid: Critical Analysis of Pop Phenomena, a weekly audio podcast dedicated "to furthering knowledge by blasting away the widespread pseudosciences that infect popular culture, and replacing them with evidence-based scientific reality." He is also the...
  
  , Skeptoid: Critical Analysis of Pop Phenomena
  Skeptoid
  Skeptoid is a weekly podcast created and hosted by American skeptic and author Brian Dunning. The show follows an audio essay format, and is dedicated to the critical examination of pseudoscience and the paranormal....
  
  .