It needless you will see him for him to see you, enough that crosses the two lines of his visor to remove you at lightning speed.
Snipers are sort of ghosts walking airsoft fields without anyone being aware of them, growing it all eliminations and that if it were not thanks to videos like these, one would have seen deleted:
Airsoft Sniper Gameplay - Scope Cam - Sneaking up the River
N°5 Sniper Airsoft Scope cam bolt 450fps VaVAnN
Airsoft Sniper Scope Cam Bolt 500 fps #1
Airsoft Sniper Gameplay - Scope Cam - Urban Sniper 2