| 摘要 |
Apparatus, and an accompanying method, for use in a photographic camera for determining a lens aperture value for use during a fill flash exposure of a scene wherein the aperture value will impart a sufficient depth-of-field to a photographed image of the scene to capture both near and distant (background) subjects therein with pre-defined, typically ISO normal, exposures. Specifically, minimum and maximum aperture limit values are first determined from the permissible fastest and slowest shutter speeds that can be used to provide an ISO normal exposure of the distant subject. The fastest shutter speed is the fastest shutter speed to which a flash unit in use can be synchronized, while the slowest shutter speed is governed by the focal length of the lens in use. Given these maximum and minimum aperture limit values, the lens aperture to use for the fill flash exposure is determined as that which, based upon the distance of the near subject to the camera and a guide number of the flash unit, will provide an ISO normal exposure of the near subject and is equal to either the maximum or minimum aperture limit value or lies between these two limit values.
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