How does electronic flash work?
Summarise as steps or dot points
Describe/define electronic flash synchronisation
Identify your camera’s synchronisation speed.
Electric energy, is converted to high voltage and used to
charge a capacitor. The high pitch noise often heard is the convertor working. The
capacitor is permanently connected to two electrodes in a glass tube
("bulb") filled with xenon gas. At this stage, the gas does not
conduct electricity and emits no light.
Another smaller capacitor is charged along side the large
one, and when the flash unit is directed to fire, the smaller capacitor discharges
through a transformer, which generates a pulse of very high voltage.
This voltage is applied to a third electrode in the xenon
tube. The high-voltage pulse causes the gas to ionize. Ionization makes the gas
conductive, and the big capacitor starts to discharge through the xenon gas.
Bright light is emitted by the xenon gas during this process.
Since the resistance of the gas is very low at this stage, the discharge is
rapid, with the current following an exponential curve.
About 1/1000 - 1/200 seconds later the capacitor is
essentially empty, and the voltage has dropped so low that the xenon stops to
conduct electricity, and the light pulse dies off. At this point, the process
can be started from the beginning.
The flash itself has a very short duration (1/1000 seconds or
less). For proper exposure, the shutter must not block any part of the frame at
the instant the flash is fired. Otherwise, part of the frame will not
"see" the flash and will not be exposed. Therefore, flash should be
used at shutter speeds which are long enough to include a moment where the
whole frame is uncovered. The highest speed at which this is possible is called
the top or highest synchronization speed of the camera. Flash
photography is possible with this shutter speed and with all longer ones as
well.
My camera’s sync speed is 1/200 of a second.
Direct copy from this
website. Due to the complexity and my utter confusion in some parts of this
flash explanation, I could not put this into my own words.
http://www.chem.helsinki.fi/~toomas/photo/flash-faq.html
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