Electronic Mirror Shutter - ARRI ALEXA Series User Manual

188 ALEXA Studio

15.2.1 Electronic Mirror Shutter

The electronic mirror shutter is located between the PL-mount and the
image sensor at an angle of about 45°. It is part of the optical reflex
viewfinder system that reflects the lens image into the optical
viewfinder.
It is synchronized with the electronic shutter of the camera sensor so
that the sensor is only read out in the dark phase. This completely
removes rolling shutter effects of the sensor readout.
Its 180° mirrored surface reflects the lens image into the optical
viewfinder. The open sector of the mirror shutter can be reduced
through an electronically controlled sector gate. The mirror shutter
rotates 360° for every capured frame, controlling the exposure of the
sensor through its open sector. The readout of the sensor happens
while the mirror reflects the light of the optical path into the optical
viewfinder.
The angle of the open sector is electronically controlled via the regular
camera controls.