In the context of aviation and aerospace, "Automatic Brightness Control" (ABC) refers to a feature that automatically adjusts the brightness of cockpit displays, instruments, and lighting systems in response to changing ambient light conditions. This is typically done to:

1. Reduce pilot workload: By automatically adjusting brightness, pilots don't need to manually adjust display settings, allowing them to focus on flying the aircraft.
2. Improve visibility: ABC helps to optimize display visibility in varying light conditions, reducing glare and improving readability.
3. Enhance night vision: By adjusting display brightness to match the ambient light, ABC helps to preserve pilots' night vision, making it easier for them to see outside the cockpit at night.
4. Reduce eye strain: Automatic brightness control can help reduce the strain on pilots' eyes caused by constantly adjusting to changing light conditions.

ABC is often implemented using sensors that detect the ambient light level and adjust the display brightness accordingly. This feature is commonly found in modern aircraft, including commercial airliners, business jets, and military aircraft.