Metz 28 AF-4 C - Manual (Page 28)

5. TTL flash control
28
The mecablitz receives its information exclusive-
ly from the connected TTL-controlled camera.
Exposure measurement in TTL mode (TTL = through-
the-lens) is completed by the camera’s sensor. This
sensor measures the light reaching the film through
the camera lens. An electronic control
circuit within the camera transmits a stop signal to
the flashgun as soon as the film has been exposed by
the correct amount of light; the flash is then instant-
ly cut out. The advantage of the TTL mode is that all
factors influencing the exposure of the film (such as
filters, change of aperture or variable aperture
zooms) are taken into account. You need not worry
about adjustment of the light output. The camera’s
electronic system automatically defines the required
amount of light. You can also utilize various metering
facilities (e.g. spot , matrix or centre-weighted
overall readings) offered by some cameras.
The maximum range for the selected aperture is
indicated underneath the f-stop on the aperture
calculator. Example: With ISO 100 and f/4 the maxi-
mum flash range is 7 m (see fig. 3). The minimum
lighting distance equals approximately 15% of the
maximum flash range.
If the actual distance is shorter than the
minimum lighting distance, then this may
result in overexposure.
A strip of film must be loaded in the camera if tests
are to be conducted in TTL flash mode. The effective
flash range can only be checked by the correct-expo-
sure display (o.k.) if the flash is triggered by the
camera and not with the manual release on the flash-
gun!
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