10 Automatic flash sync
speed control
Depending on the camera model and
camera mode, the shutter speed is
switched to flash sync speed when
flash readiness is reached (see the
camera's operating instructions).
Various cameras have a sync speed
range, for example from 1/60 sec to
1/250 sec (see the camera's operating
instructions).
Shutter speeds slower than the flash
sync speed can be set according to the
camera mode and the selected flash
synchronisation.
If a camera with a between-the-lens
shutter is used, flash sync speed is not
controlled automatically. As a result,
the flash can be used at all shutter
speeds.
10.1 Automatic high-speed syn-
chronisation (HSS)
Various cameras support automatic
high-speed synchronisation (see the
camera's operating instructions). This
flash mode makes it possible to use a
flash unit even with shutter speeds that
are faster than the flash sync speed.
Interesting results may by achieved in
this mode when, for example, a wide
open aperture (e.g., f/2.0) is used to
limit the depth of field in portrait shots
taken in very bright ambient light. The
flash unit supports high-speed syn-
chronisation in TTL and M flash modes
(depending on the type of camera).
For physical reasons, however, high-
speed synchronisation significantly
reduces the number and the maximum
flash range.
High-speed synchronisation is activat-
ed automatically if a shutter speed
faster than the flash sync speed is set
+
on the camera, whether manually or
automatically by the exposure program.
Note that in the case of high speed syn-
chronisation the guide number of the
flash unit also depends on the shutter
speed.
The faster the shutter speed, the lower
the guide number!
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