Leica M Instruction Manual page 197

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 Leica M 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
– when using the flash unit on the camera or with the SCA adapter
set
– 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 main menu (see p. 154/246) select
(page 1, section), and
CAMERA
2. Select the desired option in the sub-menu.
195
Flash Sync. Mode