Light-flash effects have also been documented which are of a duration sufficient to be misperceived as continuous. Photo (OP-2) is an example, taken on Tri-X film, 300 mm telephoto, f4, wherein the flash rate was approximately 30 times per second, but the UFO was perceived as a steady light source. P.S.I. has other examples of this phenomenon, re-corded on color film.

PHOTO OP-2: Section of 35 mm time exposure, of 11/11/74, spherical UFO with light pulse   approximately 30 per second. Glow appeared steady to all observers.