(Tests done in November 2012)

Camera settings
+ remote flash
+ internal flash as controller only
+ channel 1


At t=0 
Sequence starts with a burst of approximately 50uS

t=4.394mS (depends on channel)
Camera flashes another burst of approx 50uS to command the slave to transmit a measuring preflsah


t=4.54mS
Slave flash starts the preflash illumination to measure the scene
The intensity is reduced to about 16% of the brighntess that it will illuminate when exposing the photo

t=5.814mS 
The preflash illumination ends


t=75.312
The camera transmits three bursts spaced a few milliseconds apart. Each burst is about 40uS long
The interval between the flashes provides information to the slave flash on how much light it should provide
These intervals are analysed in the excel sheet
The interval between the first and second pulse seems to indicate the amount of light needed
The interval between the second and third pulse seems to indicate the light output that the flash will actually be able to provide

t=?
Some time around here the mirror lifts and the shutter starts to open (observed on high speed camera but not measured)

t=?
The shutter is now fully open (observed on high speed camera but not measured)

t=143.46mS
Camera transmits a 40uS pulse to signal to the slave flash to start illumination

t=144mS
Flash illuminates at full intensity for the duration requested by the camera (the pulses of t=75mS)




Interval between first burst and preflash command depends on the channel number:
Ch1 4.394mS 
Ch2 4.592mS
Ch3 4.190mS
ch4 4.788mS


The interval between the 1st and second pulses of the 3 pulse message dictate the amount of light the flash would need to produce for the actual exposure
The interval in mS is given by 0.4436 Log(required/preflash) + 2.8  
Where required/preflash is how many time brighter the exposure flash has to be compared to the preflash.