Abstract: A polarity insensitive flash driver circuit for use in a photographic system including a camera for generating a flash trigger signal, and an electronic flash unit having a trigger circuit actuatable responsive to the flash trigger signal to initiate a flash illumination. This flash driver circuit includes a two conductor, polarity insensitive connector for connection to the flash driver circuit. A first gate controlled rectifier is connected between the two conductors for controllably conducting a current in a first polarity. A second gate controlled rectifier is connected between the two conductors for controllably conducting a current in a second polarity. Actuating means responsive to the flash trigger signal simultaneously actuate the first and second gate controlled rectifiers to conduct a current.

Abstract: A video transfer stand generates a video signal from a front-illuminated image on a semi-transparent or translucent original, especially a photographic print. The video system, including the transfer stand and a video display connected to the stand, produces output video contrast as a function of the transfer characteristic (gamma) of the video system as it interacts with the contrast exhibited by the reflection density of the print. This interaction produces high contrast that blocks out details especially in shadow areas of the video display. Such undesirably high contrast is moderated--releasing shadow detail--by variably backlighting the print in the transfer stand. The rear illumination, which is adjusted in view of the display, produces inherently lower contrast than the reflected illumination and, in combination therewith, optimizes the video display contrast.