Metz 34 AF-3M TTL flash control, With automatic film speed setting DX ISO 32/16

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°

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