Metz 28 AF-4 N operating instructions TTL flash control

5. TTL flash control

6The 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 filters, change of aperture or variable aperture zooms) are taken into account. You need not worry about adjust- ment 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 maximum 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 k 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 flashgun!

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