Abstract: A transmissometer includes electronic shutters for interrupting the transmitted and reference light beams at selected locations and at selected time intervals for establishing the various modes of operation of the transmissometer. The electronic shutters take the form of liquid crystal displays that are selectively energizable to either a clear or an opaque condition. The transmissometer also includes an electronic stepwise light attenuator located in the path of the light beams. The attenuator includes a body and multiple liquid crystal display segments uniformly distributed throughout the body, with the segments being independently energizable to provide stepwise opacity.