What is the purpose of turning off specific lights before entering the flight deck?

Turning off specific lights before entering the flight deck is primarily aimed at preventing glare on instruments. In an aircraft cockpit, ambient lighting can reflect off various surfaces and interfere with the visibility of critical instruments. By reducing glare, pilots can ensure that they have a clear view of their readings and displays, which is crucial for maintaining situational awareness and ensuring safe operations, especially during critical phases of flight such as takeoff and landing.

While energy conservation, safety compliance, and passenger awareness are important considerations in the context of aviation operations, the primary rationale for this specific action is to enhance visibility and ensure that pilots can effectively interpret the necessary flight data without distractions or obstructions.