Leica M Operating Instructions Manual page 163

SELECTING THE FIRING MOMENT
Flash photographs are illuminated by two light sources, the
available light and the light from the flash. Parts of the subject that
are exclusively or primarily illuminated by the flash are almost
always reproduced sharply (with correct focusing) due to the
extremely fast pulse of light. By contrast, all other parts of the
subject – those that are sufficiently illuminated by the available
light or illuminate themselves – are portrayed with different
degrees of sharpness in the same picture. Whether these parts of
the subject are reproduced sharply or "blurred", and the degree of
blurring, is determined by two independent factors:
1. The shutter speed, i.e. for how long these parts of the subject
"act upon" the sensor, and
2. how quickly these parts of the subject – or the camera itself
– are moving during exposure.
The longer the exposure time or the faster this movement, the
greater the extent to which the two – superimposed – parts of the
picture can differ.
With the conventional time for firing the flash, at the beginning of
the exposure, i.e. immediately after the 1st shutter curtain has
completely opened the image window. This can actually lead to
visible contradictions, e.g. in the picture of the motorcycle, which
is being overtaken by its own light trail.
The camera allows you to choose between this conventional firing
moment and synchronization with the end of the exposure, i.e.
immediately before the 2nd shutter curtain starts to close the
image window again. In this case, the sharp image reflects the end
of the movement captured. In the photograph, this flash technique
gives a natural impression of movement and dynamics.
The function is available
– for all camera and flash unit settings
– in aperture priority mode and with manual shutter speed
selection
– in automatic and manual flash mode.
The displays are identical in both cases.
Setting the function
1. In the picture parameters menu, select
there , and
Flash Sync. Mode
2. select the desired option in the sub-menu.
and
Flash Settings
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