I recall being told that it takes a dark adapted eye thirty minutes to recover from the flare of a one lighted match. Night vision is sensitive! The best way to get it is to simply walk into the twilight. Most trails stand out more under natural night light than they do under illumination. It is amazing how much you can see by starlight, away from the city, at least. By a full moon, you can read the newspaper.<br><br>Still, there are times when you have to accept the "tunnel of light" brought on by lamps - precipitous terrain for one. I find that when I do use a headlamp, it is best carried in the hand. Ground relief stand out more and I have better depth perception. My preferred light for night use is the now virtually obsolete carbide lamp. It provides a broader beam with less spotlight effect and is perhaps somewhat less destructive of night vision than the typical electric job. Makes a dandy hand warmer and fire starter as well.<br><br>What to do when other require a light and you don't?<br>One solution is to put the person requiring the light toward the back of the group. You will retain a little of your night vision in this manner. Closing one eye has worked, rather awkwardly, for me as well.