Sony HVL-F56AM Operating Instructions Manual page 34

TTL flash
Manual flash provides a fixed flash intensity irrespective of the
brightness of the subject and the camera setting. TTL* flash measures
the light from the subject that is reflected through the lens.
Some cameras enable P-TTL metering, which adds pre-flash to TTL
metering, and ADI metering, which adds distance data to the P-TTL
metering.
This flash defines all P-TTL and ADI metering as TTL flash and
displays
*TTL = through the lens
• ADI metering is possible in combination with a lens with a built-in
distance encoder.
Before using the ADI metering function, check whether your lens
has a built-in distance encoder by referring to the specifications in
the operating instructions supplied with your lens.
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on the data panel.