Leica R9 Instructions Manual page 187

When using aperture priority mode, the camera
calculates the necessary time automatically,
depending on the number of flashes and the
flash frequency. If this would lead to overexpo-
sure due to the available light, the shutter speed
display flashes.
For a successful strobe photograph, for example
when several phases of one sequence of move-
ment are recorded on one picture, the operating
range of the flash unit, the number of flashes,
the distance and of course the aperture are of
crucial importance. You can find information
about this in the instructions for your flash unit.
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