APPLICATION:
Wide areas viewed from a high or wall-edge mount where you want one half of the field and a clean cut-off on the other - corridors, lobbies, open-plan rooms and larger suites.

APERTURE GEOMETRY: 
Half-disc (D-shaped) aperture - masks the lens along a straight edge.

BEHAVIOUR:
The sensor sees one half of its native field - full width on one side of the cut line, nothing on the other. With the flat edge horizontal it covers everything below (or above) the centre line; rotate the cover and the same half-field turns to one side.