CPES

Ghost, spirits or dust?

Many believe they have captured the presence of a spirit or ghost due to the “orbs” that appeared in a photograph or even video. In most incidents this is simply not the case. The two most common sources for “orbs” are Lens Flare and Backscatter. Let’s discuss each of these phenomena.

Lens flare refers to a phenomenon wherein light is scattered or flared in a lens system, often in response to a bright light, producing a sometimes-undesirable artifact within the image. This happens through light scattered by the imaging mechanism itself, for example through internal reflection and scattering from material imperfections in the lens. Lenses with large numbers of elements such as zooms tend to exhibit greater lens flare, as they contain a relatively large number of interfaces at which internal scattering may occur. These mechanisms differ from the focused image generation mechanism, which depends on rays from the refraction of light from the subject itself.

There is always a certain amount of dust floating around in the air. You may have noticed this at the movies when you look up at the light coming from the movie projector and notice the bright sparks floating around in the beam. In the same way, there are always dust particles floating around nearby when you take pictures or use a video camera. This brings us to Backscattering.

In physics, backscatter (or backscattering) is the reflection of waves, particles, or signals back to the direction from which they came. It is usually a diffuse reflection due to scattering, as opposed to specular reflection as from a mirror, although specular backscattering can occur at normal incidence with a surface. Backscattering has important applications in astronomy, photography, and medical ultrasonography. 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. They can also be caused by 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 spectra, purple fringing or other chromatic aberration. With rain droplets, an image may capture light passing through the droplet creating a small rainbow effect.