Polaroid 636 Repair Manual page 11

5. With the solenoid deenergized and the walking beam free of the shutter latch, spring-
action opens the shutter blades. The internal clock is running and the photocell starts to
measure light.
6. In a fill-flash exposure, when the photocell sees 75% of the light needed for a proper
exposure, it signals the flash to fire. The flash provides the remaining 25% of the
necessary light. Note that in a fill-flash exposure, the photocell always beats the internal
clock in ordering flash fire.
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