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5. TTL flash control
The mecablitz receives its information exclusively
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 instantly cut out.
The advantage of the TTL mode is that all factors
influencing the exposure of the film (such as fil-
ters, 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 requi-
red amount of light. You can also utilize various
metering facilities
(e.g. spot , matrix or centre-
weighted overall readings)
offered by some came-
ras.
The table on page 37 gives the maximum range
for the selected aperture. The minimum lighting
distance is approx. 15% of the maximum thres-
hold range.
If the actual distance is shorter than the
minimum lighting distance, then this may
result in overexposure.
The speed of films to be exposed under
TTL flash control must be between ISO
25/15°* and ISO 1000/31°. Correct expo-
sures cannot be guaranteed with other
film speeds.
A strip of film must be loaded in the camera if tests
are to be conducted in TTL flash mode. The effec-
tive flash range can only be checked by the cor-
rect-exposure display (o.k.) if the flash is triggered
by the camera and not with the manual release on
the flashgun!
*
With automatic film speed setting (DX): ISO 32/16°
9