No light is no problem with night vision. These devices - available in binocular, monocular, riflescope, and more versions, are great for tactical situations or everyday use. Depending on the system in the device, you'll either have a system of Image Intensifier Tubes - commonly abbreviated ITT - or a digital system, both of which enhance light to give you a picture of what's going on in the dark.
Night vision devices often use infrared illuminators to enhance the picture that you are shown, but others will use the natural light from the environment. In a tactical situation, the edge that night vision gives is obvious - where others are blind, a night vision device helps with shot placement and overall tactical awareness. Choose from brands like Armasight, ATN and more for the best in tactical night vision!