True or False: Both eyes must remain open during the entire focusing procedure.

Keeping both eyes open during the focusing procedure is essential because it allows for depth perception and a more natural visual experience. When both eyes are used, the brain can process the images from each eye, helping to provide a clearer view and reduce the chances of eye strain. This is particularly important in night vision scenarios, where maintaining situational awareness and the ability to perceive distances accurately can affect safety and effectiveness in low-light conditions. Using both eyes enables users to adapt better to varying light levels and enhances the overall effectiveness of the night vision equipment. Therefore, the assertion that both eyes must remain open during focusing is true.