Photron Fastcam SA2, Hardware Manual

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Chapter. 3 Recording
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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.
When the camera is set to the normal RANDOM mode (the same as START mode) and RANDOM
RESET mode, the difference in the recording operation for the trigger input is shown graphically.
In the normal RANDOM mode 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 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 exposure starts anew. For this reason, the trigger input time and the timing of
the start point of the first frame are constant. The interval from when the trigger is input until the
exposure begins is approximately 0.7 us.