“Scintillation” — the granular, snowy appearance in night vision imagery — is a normal characteristic of image intensifier tubes, not a defect.

The effect appears because the photocathode and MCP are amplifying individual photons. At very low light levels, there are fewer photons to work with, so individual photon events appear as bright spots. At higher light levels (more ambient light), the scintillation decreases and the image appears smoother.

If the image is grainy in conditions where it shouldn’t be:

•        Low ambient light without IR illumination — add an IR illuminator

•        Dirty or fogged optics — clean the objective and eyepiece lenses

•        Automatic brightness control struggling with the scene — avoid bright light sources in the field of view

For digital devices, grain has a different cause: high ISO amplification of a weak sensor signal. The fix is the same — add more IR illumination to reduce the gain required.