The synchronizer 1, wherein the flash unit operates according to a flash sequence in a flash interval after actuation of the actuator, the fundus camera configured to coupled to a digital camera system including an auxiliary power supply and a shutter system having a digital camera shutter having an associated open position in a transit time consistent with the flash interval to capturing {HEAD ~ an image} at {TAIL ~ the digital camera system}, the circuit further comprising: 
The synchronizer 1 , wherein the flash unit operates according to a flash sequence in a flash interval after actuation of the actuator , the fundus camera configured to coupled to a digital camera system including an auxiliary power supply and a shutter system having a digital camera shutter having an associated open position in a transit time consistent with the flash interval to capturing { HEAD ~ an image } at { TAIL ~ the digital camera system } , the circuit further comprising :
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