The term 'Poltergeist" denotes a spiritual being that has the ability to shift and influence objects. There have been many reports of poltergeist activity taking place in homes. These incidents usually include knocking, thumping and moving of objects. There have been accounts of people being thrown about and even levitation. Ectoplasm refers to the supposed emanation from the body of a medium. In these days, it simply means mist or vapour. Ectoplasm has been captured on camera by millions of people, and the colours are usually white or dull. Humid conditions may cause this effect in photographs. Ectoplasm is not to be confused with smoke, which does not have swirls.
One of the more notorious poltergeist events is the Enfield Poltergeist happening. It took place between August 1977 and September 1978. There is a documentary on the Enfield Poltergeist event in the Footage section of this site.
Orbs are one of the most often captured objects on camera. They appear as translucent balls, and are said to be souls of the dead. At times, orbs photographed can have a 'nucleus' within it.
Some digital cameras, under the correct lighting, can capture pictures with orbs. I have once photographed a house in Vietnam with a gigantive blue orb with a nucleus within it. I have to say orbs are a beautiful work of art.
