Arri UDM-1 Ultrasonic Distance Measure This UDM-1 Ultrasonic Distance Measure Basic Set provides focus measuring data for any ARRI or other brand of camera. The UDM-1 measures the distance between the sensor/film plane and the subject or object with ultrasonic pulses. Focus tracking is enabled when using the UDM-1 with an ALEXA Plus/Studio and the UMC-4 controller. The UDM Display unit shows the distance data on an LCD screen. A sensor unit, display, and a sensor cable are included with the UDM-1 Basic Set. Mounting options are available separately.