| 摘要 |
An apparatus is described for effecting scene-brightness-dependent control of the duration of the flash produced by a flashbulb flash unit having at least one flashbulb. The apparatus includes a housing so configured and dimensioned that it can be pushed over and onto the flashbulb flash unit. The housing is provided with at least one controllable-transparency optical unit located to occupy the position in front of the flashbulb of the flash unit when the housing has been pushed into place over the flash unit. The housing furthermore contains an automatic scene-brightness-dependent flash-duration control circuit connected to the optical unit and operative for controlling the duration of the flash produced by the flashbulb by keeping the optical unit transparent for a scene-brightness-dependent exposure interval and then automatically rendering the optical unit non-transparent.
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