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10.5 Manual flash exposure corrections
The auto flash exposure mode of the flash unit, as of most cameras, is adjusted
to a reflection factor of 25% (the average reflection factor of flash subjects). A
dark background that absorbs much of the light or a highly reflective bright
background (backlit shots, for example) may result in, respectively, underexposu-
re or overexposure of the subject.
To offset these effects, the flash exposure can be adjusted manually for the shot
with a correction value. The extent of the correction depends on the contrast bet-
ween subject and background.
In TTL, E-TTL and automatic flash modes, manual flash exposure correction fac-
tors of from -3 EV (f-stops) to +3 EV (f-stops) can be adjusted on the flash unit in
1/3 step increments.
Many cameras have a setting element for exposure corrections that can also be
used in TTL flash mode. Please refer to the information in the camera’s operating
instructions.
Dark subject in front of a bright background:
Positive correction value (approxi1 to +2 f-stops EV).
Bright subject in front of a dark background:
Negative correction value (approximately -1 to -2 f-stops EV).
When a correction value is set, the flash range indicated on the flash unit display
may change as it adjusts to the correction value (depending on the type of
camera). For adjustments, see 6.4.
Manual flash exposure correction is possible in TTL flash mode only if the
camera supports this function (consult the camera’s operating instruc-
tions). If the camera does not support this function, the adjusted correction
value will have no effect. For some camera models, the manual flash
exposure corrections must be adjusted on the camera. If this is the case,
no correction value will appear on the flash unit display.
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11. Flash readiness indication
When the flash capacitor is charged, the flash readiness symbol
lights up
on the flash unit, indicating that the flash is ready to fire. This means that flash
light can be used for the next shot. Flash readiness is also transmitted to the
camera and indicated accordingly in the camera’s viewfinder (see 14).
If a shot is taken before the flash readiness indicator appears in the camera’s
viewfinder, then the flash unit will not be triggered and, if the camera has alrea-
dy switched to flash sync speed (see 12), the shot may have the wrong exposure.
The multi-zone AF measuring flash
integrated into the flash unit can be
activated by AF cameras only when flash readiness is indicated (see 18).
12. Automatic flash sync speed control
Depending on the camera model and camera mode, the shutter speed is swit-
ched to flash sync speed when flash readiness is reached (see the camera’s ope-
rating instructions).
Shutter speeds cannot be set faster than the flash sync speed, or they are swit-
ched automatically to the flash sync speed. Various cameras have a sync speed
range, for example from 1/30 sec. to 1/125 sec (see the camera’s operating
instructions). The sync speed set by the camera depends on the camera mode,
the ambient light, and the focal length of the lens used.
Shutter speeds slower than the flash sync speed can be set according to the
camera mode and the selected flash synchronisation (see also the camera’s ope-
rating instructions and 17).
If a camera with a between-the-lens shutter (see the camera’s operating
instructions) or HSS synchronisation (see 17.4) is used, flash sync speed is
not controlled automatically. As a result, the flash can be used at all shut-
ter speeds. If you need the full light output of the flash unit, you should
not select a shutter speed that is any faster than 1/125 sec.
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