Sony HVL-F58AM - Manual (Page 46)

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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.
TTL metering also has a P-TTL metering function, which adds a pre-flash to
TTL metering, and an ADI metering function, which adds distance data to the
P-TTL metering.
This flash unit defines all P-TTL and ADI metering as TTL flash and
is displayed on the LCD panel.
*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.