First i have to say that i recognized a litte glow around myself by night up to 5 meters around me.
I said this because i think this glow/light source is the reason of the following issue.

A Friend and me walking around by night with NVGs on our tactical helmets.
We was close to each other, maybe 10 - 20 meters.

When my friend deactivated his NVG, i see my view through the NVG getting brighter.
My friend had the same experience when i turned off my NVG while his NVG was activated.