Some of the patterns seem to vibrate optically, like the op art of the 1960s.
According to conspiracy theorists, CIA experts edited and optically manipulated the film to mask what had really happened.
Optically, there was little to choose between the two machines in terms of image clarity and definition.
The system uses two prisms within the lens housing to optically compensate for camera shake.
The artefacts are dated using a method called optically stimulated luminescence.
DVDs are read optically instead of mechanically.
