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p.1 #19 · p.1 #19 · Can a pair of Godox AD360 II or AD600 flashes freeze motion for sports shots? | |
Littleguy wrote:
Yes - histoically, IGBT flash units have not been the first choice for the long burn approach for high speed sync.
But with all the new battery powered units flashes being IGBT based (Godox AD360, Broncolor Siros, Profoto B1 & B2) - triggers are now coming out with timing adjustments to get the most of the shorter burn times of IGBT flashes.
Plus from the OP's question - it looks like he is trying to overpower the sun and he will most likely be at full power anyways.
If he was indoors in a low light situation - he wouldn't be asking about using a faster shutter speed to stop motion - he would be using the flash duration to stop motion.
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The adjustment capabilities in the triggers is to optimize the FP-Sync plus relative to the first curtain shutter opening. By design, FP-sync sends the fire pulse prior to first curtain opening. When designed, FP sync was for flat burn flash bulbs and slow cloth focal plane shutters. The pulse earlier than shutter opening was to give the bulb time to reach maximum output prior to the curtain opening.
New, metal focal plane shutters are much faster, optimizing the relationship between the pulse and the shutter opening minimizes the gradient caused by the decreasing light output as the capacitor loses voltage pressure.
The timing adjustment also permits optimizing the fire signal to get better use of the diminishing tail for a voltage controlled strobe when used for "long burn".
IGBT, without the HSS rapid pulsing implementation, has no tail below full power. A 1/10,000 flash duration will never be able to illuminate the sensor during the travel of a focal plane shutter slit at any speed above x sync. Without access to the engineering documents for a camera the best estimate for the length of time necessary for the shutter curtains to travel across the sensor is the x sync speed. i.e. if x sync is 1/200 then the shutter takes 1/200th of a second to travel across the sensor at all shutter speeds above x sync. The faster nominal shutter speed results from the width of the slit as both shutter curtains travel across the sensor. That means that for FP sync to work; a) the fire pulse has to turn on the light before the front curtains starts to expose the sensor; b) the light has to continue, at the same intensity, for the duration of the shutter travel until the rear curtain covers the sensor.
Whether using "long burn" or HSS, when using FP-sync the shutter becomes the action stopping mechanism because the light is now a constant source for the duration of the shutter travel.
Simply put, x sync the flash duration determines action stopping, FP sync the shutter determines action stopping.
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