Sigma FP User Manual page 58

The mode is changed to "Evaluative" that focuses on the detected face.

If multiple people's faces are detected, the detection frame is displayed

for the face that appears to be the nearest.
CAUTION
[Face / Eye Detection AF] is not available in MF mode.

The face/eye detection may fail in the following cases:

A part of the face is covered by sunglasses, a hat, bangs, etc.
●
The scene is dark or backlit.
●
The subject is out of focus.
●
The subject is moving quickly.
●
If face detection fails, the face is focused on using the selected focus

frame.
FOCUS LIMITER
Limits the focus operating range to accelerate the AF speed.
[ / SHOOT] → [Focus] → [Focus Limiter]
or [ / SHOOT] → [Lens Function Settings] → [Focus Limiter]
Off (Default)
Near Side
On
Far Side
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When a face and an eye are detected, the
orange detection frame is displayed.
When the detected face and eye are
focused
half-pressed, the detection frame changes
to green.
Does not limit the operating range.
The focus operates only on the near side from
almost at the center.
The focus operates only on the far side from
almost at the center.
after the shutter button is