Eye Adaptation Shooting Technique
Dark adaptation: Initial poor vision due to your eyes adjusting from a bright environment to a dark environment.
Light adaptation: Initial poor vision due to your eyes adjusting from a dark environment to a bright environment.
GTC Instruction: When engaging a target minimize yours eyes light dark adaptation process by engaging the portion of the target that has similar light levels to which your eyes are currently adjusted to, i.e. coming from a bright environment, engage the brighter portion of your target.
In a neutral environment the human eye will focus quicker on the darker area