Sometimes, as shown here, several similar photographs appear during a session. Dr. Eisenbud call these images a theme.

The photos vary because the tiny optical device is not in the same position in front of the Polaroid camera lens during the several exposures, all of which are made before the first one has time to develop and become visible to the audience.

In the meantime the optical device can be slipped out of the gismoand secluded.