This allows the user to see more detail, but with no color differential. Changing illumination can affect visual acuity. Looking at the moon with an NVG is comparable to looking directly at the midday sun with the naked eye. This could result in glare, flashblindness, and afterimage. Particularly troublesome is ensuring that aircraft and cockpit lights are NVG-compatible.
Incompatible lights make the outside scene less visible with NVGs.
Changing cockpit lights to be NVG-compatible is very complicated and expensive. The Federal Aviation Administration requires operators to use aircraft position and anti-collision lights. Such flickering or flashing lights can cause operational problems for NVG wearers. Low-light levels inherently produce decreased visual resolution, acuity, and contrast, making hazard detection more difficult. Even with NVGs, all of these limitations will still be present.