21. At this point, the blades are still open and the exposure is being made. The photocell

continues measuring light which now includes the light bouncing back from the flash. Next, the camera must decide when to shut down the flash and when to close the shutter blades.

22. In the high ambient (Fill Flash) mode, the photocell makes the decision to shut down the flash and close the shutter blades. It does this when it sees the remaining 25% of the light required for a proper exposure. (This light is provided by the flash.) The camera logic signals the flash to quench and commands the solenoid to close the blades.

23. The next condition in which a flash exposure can be made is in a low ambient condition (low light level, outdoor scenes and all indoor scenes). In this condition, there is so little light that the clock beats the photocell in the race to fire the flash. When the clock reaches 74 milliseconds (ms), the flash is fired.

Mors Than 50% = near Less Than 50% = far

26. If the measurement is equal to or more than 50% of the light needed for a proper exposure, the camera senses subject is NEAR. If the measurement is less than 50% of the light needed for a proper exposure, the camera senses that the subject is FAR.