Leica M Instruction Manual page 67

Notes:
Studio flash systems may have a very long burning time. Therefore,
when using them it may be useful to select a slower shutter speed
than / s.
1
180
The same applies to radio controlled flash triggers for "unchained
flash", as the radio transmission can cause a delay.
The following sections describe only those settings and functions
that are available when using the Leica M with system compatible
flash units.
An exposure compensation set on the camera (see p. 184) only
influences the measurement of available light. If you want to
simultaneously use compensation of the TTL flash exposure
metering in flash mode – in parallel or in the opposite direction,
you must make this additional setting (on the flash unit).
More details of flash use, in particular for other flash units not
specially adapted to the Leica M and for different flash modes can
be found in the relevant manuals.
Settings for camera-controlled automatic flash mode
After the flash unit in use has been turned on and set to the operating
mode for GNC (= Guide Number Control), the following actions on the
Leica M are necessary:
1. Before taking each flash picture the exposure metering is first
performed by gently pressing the shutter release, so that the
display in the viewfinder shows the shutter speed or switches to
the light balance. If this stage is missed out by fully depressing
the shutter release in one quick movement, the flash unit will not
fire even if required.
2. The shutter speed dial must be set to
( / s), or to a slower shutter speed (including
1
180
priority mode, the camera automatically switches to the flash
sync speed set in the menu or the speed range (see "Selecting
the sync speed/the sync speed range", p. 194). The shortest
flash sync speed must be taken into account as this determines
whether a "normal" flash is fired or an HSS flash (see p. 194).
3. The desired aperture, or the aperture required for the relevant
distance to the subject, must be set.
192
, to the flash sync speed
A
). In aperture
B