Spectral viewers are glasses with special lenses that allow their wearers to see ghosts. Ghosts can usually only be seen through spectral viewers, though there have been several exceptions.
In the 1960 film, the spectral viewers were invented by Dr. Plato Zorba as a method of seeing spirits. After Dr. Zorba was murdered by Benjamin Rush and the former's nephew Cyrus inherited his mansion, he and his family used the spectral viewers to see the 12 ghosts haunting the house.
In this film, the spectral viewers are large and resemble goggles. They are also dangerous, as when a fly flew by a pair of spectral viewers, the viewers electrocuted and killed it. At the end of the film, with all of the imprisoned ghosts having been released, what appeared to be Elaine destroyed the spectral viewers via telekinesis.
The spectral viewers of the remake were used to see ghosts, originally by Cyrus Kriticos' ghost-hunting team and the Spirit Reclamation Business. When Arthur, his family, Dennis, Kalina and Maggie were locked in the mansion, they used the spectral viewers to see the rampant ghosts that have been released. In the remake, the revised viewers are smaller, had lights along the peripheral corners, and closely resembled plastic glasses.
It has not been revealed in any of the films just how the spectral viewers actually worked. The 1960 version resembled goggles set in a frame with an electrical circuit going through them while the 2001 version resembled a set of plastic glasses. Theories as to how they operated include:
- The lens were treated chemically or on a molecular level to perceive light in the invisible spectrum.
- The lens alter a person's perception of light as it strikes objects (a ghost, in this case) in a way to perceive ghosts in an invisible state similar to how corrective lenses bend and refract the light hitting a person's eye, improving visual clarity.
- The lens are comprised of a material that somehow operate on the same ethereal plane as the spirits.
- Sometimes, the spectral viewers aren't really necessary to see the ghosts; Cyrus saw them in the 2001 remake when they came after him. However, he might have just felt other indications that they were coming after him (i.e. temperature, sensitivity...).