Exposure control device for a camera in flash photography

• US 4,690,536 A
• Filed: 09/09/1986
• Issued: 09/01/1987
• Est. Priority Date: 09/09/1985
• Status: Expired due to Fees

• Current Assignee: Minolta Camera Kabushiki Kaisha
• Original Assignee: Minolta Camera Kabushiki Kaisha
• Inventors: Nakai, Masaaki, Taniguchi, Nobuyuki, Yamaki, Toshio, Mukai, Hiromu, Fujino, Akihiko, Izumi, Shuji
• Primary Examiner(s): PERKEY, WILLIAM B
• Application Number:
  US06/905,160
• Time in Patent Office: 357 Days
• Field of Search: 354/400, 354/402, 354/414, 354/416, 354/417, 354/420, 354/421, 354/422, 354/429, 354/431, 354/432, 354/433, 354/434
• US Class Current: 396/130
• CPC Class Codes: G03B 7/08 Control effected solely on the basis of the response, to the intensity of the light received by the camera, of a built-in light-sensitive device
• CPC Class Codes: G03B 7/093 for control of exposure time
• CPC Class Codes: G03B 7/16 in accordance with both the intensity of the flash source and the distance of the flash source from the object, e.g. in accordance with the "guide number" of the flash bulb and the focusing of the camera
• CPC Class Codes: G03B 7/28 Circuitry to measure or to take account of the object contrast

Abstract

An exposure control device for a camera in flash photography comprising;

first means for measuring light from a central area of an object field; second means for measuring light from another area surrounding the central area; means responsive to said first and second measuring means for detecting a rear light condition; means for controlling exposure in response to said second measuring means to cause an over-exposure by a given value when said detecting means detects the back light condition; means for directing a flash light emission; and means for integrating light reflected from the object field upon the flash light emission to stop the flash light emission when the integrated light reaches a predetermined level.

Claims

1. An exposure control device for a camera in flash photography comprising;

first means for measuring light from a central area of an object field;

second means for measuring light from another area surrounding the central area;

means responsive to said first and second measuring means for detecting a rear light condition;

means for controlling exposure in response to said second measuring means to cause an over-exposure by a given value when said detecting means detects the back light condition;

means for directing a flash light emission; and

means for integrating light reflected from the object field upon the flash light emission to stop the flash light emission when the integrated light reaches a predetermined level.

2. The exposure control device according to claim 1, wherein said detecting means includes means for comparing a light measuring output from said first measuring means with that from said second measuring means to determine a difference, and means for deciding the back light condition when the difference exceeds a predetermined level, and wherein said controlling means includes means for varying the given value in accordance with the difference of said comparing means.

3. The exposure control device according to claim 1, further comprising means for investigating focus to at least a portion within said central area, means for adjusting focus in response to said investigating means, means for disabling said adjusting means once said investigating means decides an in-focus condition even if said investigating means detects an out-of-focus condition afterward, and means for generating a modifying signal in response to said investigating means upon exposure, wherein said integrating means includes means for taking the modifying signal into consideration in stopping the flash light emission.

4. An exposure control device for a camera in flash photography comprising;

first means for measuring light from a central area of an object field;

second means for measuring light from another area surrounding the central area;

means for comparing a light measuring output from said first measuring means with that from said second measuring means to determine a difference therebetween;

means for controlling exposure in response to said second measuring means to cause an over-exposure by a given value when the difference determined by said comparing means exceeds a predetermined level;

means for directing a flash light emission; and

means for integrating light reflected from the object field upon the flash light emission to stop the flash light emission when the integrated light reaches a predetermined level.

5. The exposure control device according to claim 4, wherein said controlling means includes means for modifying the light measuring signal from said second measuring means by the given value in controlling the exposure.

6. An exposure control device for a camera in flash photography comprising;

means for investigating focus to a portion of an object field;

means for adjusting focus in response to said investigating means;

means for disabling said adjusting means once said investigating means decides an in-focus condition even if said investigating means detects an out-of-focus condition afterward;

means for directing a flash light emission;

means for integrating light reflected from the object field upon the flash light emission;

means for generating a modifying signal in response to said investigating means upon exposure; and

means for causing the flash light emission to stop in response to said integrating means and said modifying signal.