Which of the following is NOT one of the four operational defects?

The correct answer is that image distortion is not considered one of the four operational defects associated with night vision devices. The term "operational defects" generally refers to specific issues that can negatively affect the performance and reliability of night vision goggles.

Shading refers to areas of reduced brightness in the field of view, often due to imperfect optics or manufacturing defects. This can hinder visibility and situational awareness. Emission points are bright spots or flecks that can appear in the image, potentially distracting the user and impacting their ability to see clearly. Flashing or flickering occurs when the device experiences fluctuations in brightness or intermittency in the image output, which can be disorienting or cause loss of focus.

In contrast, while image distortion can occur and affect the quality of the image produced by night vision devices, it isn’t classified among the core operational defects. This distinction is significant, as it helps users and operators identify and troubleshoot issues without conflating similar yet distinct concepts in night vision technology.