Photron Fastcam BC2 HD, Hardware Manual

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25 FASTCAM BC2 HD Hardware Manual
3.5.6. RANDOM RESET Mode
RANDOM RESET mode is explained here by comparing its operation with the normal mode.
RANDOM RESET mode is a mode to improve the temporal accuracy of the record start timing and
the timing of the trigger input, where, to put it simply, with the input of the trigger signal, at the timing
that it is input, the camera’s record timing is reset.
The diagram above illustrates the recording operation (timing) difference for the trigger input when
the camera is set to normal RANDOM mode (START mode is the same) and RANDOM RESET
mode.
In normal RANDOM and START mode, the camera starts recording when the trigger is input, but
the internal record timing signal is independent and it operates regardless of when the trigger is
input. For this reason, there may be situations where the exposure start time of the first frame when
the trigger is input is advanced almost a full frame. The range of this overlap also cannot be known.
On the other hand, in RANDOM RESET mode, the camera’s internal record timing signal is reset
by the trigger input and operates anew. For this reason, the trigger input time and when the first
frame’s exposure starts are the same. The interval from when the trigger is input until the exposure
beings is approximately 2.5
μ sec.
Trigger Signal (TRIGGER IN)
▪
RANDOM Mode Operation
Record Timing Signal
(Vertical Synchronization Signal)
Recorded Frames ① ② ③ ④ ⑤
The camera’s internal record timing signal (vertical synchronization signal) is not changed for the trigger signal input.
The frame exposed when the trigger signal is input is recorded as the first frame.
A deviance occurs between the trigger signal and the internal frame timing.
▪
RANDOM RESET Mode Operation
Record Timing Signal
(Vertical Synchronization Signal)
Recorded Frames ① ② ③ ④
The record timing signal (vertical synchronization signal) is reset by the trigger input.