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I thought of my experiences with night vision when I happened upon this essay (Into the Night).
To stay in best health, I do a two-hour, six mile walk every day. In the summer (when the days are hot) and the winter (when the days are very short), I often choose the night for this activity - and I never use a flashlight.
Here is how Cornell describes dark adaptation:
There is also this notion that human night vision is not up to snuff in comparison to many other animals - specifically those with retinas that feature a Tapetum Lucidum (TL). The TL retro-reflects light back through the retina giving the it a second chance to catch the photons. It is estimated to boost a cats light collecting power by 44%. I can't compare myself to a cat, but on occasions when I have walked a dog into the dusk, as darkness falls, the dog starts to strictly follow my lead - and if left without my direction, sits. And I would point this out: if my iris opens to a diameter that is at least 20% more than the dogs, I have at least that 44% advantage advertised for the TL.
Why not a flashlight? If you don't trust the terrain, you might need a flashlight (but try trusting the terrain - especially if it's a roadway). But for me, night vision is much superior. Flashlights create long pools of light that are limited in range and are usually very tunneling. And, of course, night vision is built it - so you won't forget to bring it along.
To stay in best health, I do a two-hour, six mile walk every day. In the summer (when the days are hot) and the winter (when the days are very short), I often choose the night for this activity - and I never use a flashlight.
Here is how Cornell describes dark adaptation:
Perhaps my night vision is better than most, but I do not entirely agree with this assessment. First, if my task is to walk dark streets on a moonless night, it only me takes 5 or 10 minutes to become fully functional. And on a cloudless night with a full moon, no dark adaptation is needed - unless you keep your home incredibly well lit. Of course, my night vision may be better than average - but my vision on whole is representative of my age (66) and well below average.Humans (and most animals) can see in the “dark” only if there is some starlight or, better, moonlight. It takes some time (10 to 30 minutes) for your eyes to become dark adapted to see in such low-light conditions. Best conditions are on a night with no clouds and a full moon (try it!). When dark adapted, you can see only in black and white (no color). If there is no light at all – say in a deep cave – you cannot see anything.
There is also this notion that human night vision is not up to snuff in comparison to many other animals - specifically those with retinas that feature a Tapetum Lucidum (TL). The TL retro-reflects light back through the retina giving the it a second chance to catch the photons. It is estimated to boost a cats light collecting power by 44%. I can't compare myself to a cat, but on occasions when I have walked a dog into the dusk, as darkness falls, the dog starts to strictly follow my lead - and if left without my direction, sits. And I would point this out: if my iris opens to a diameter that is at least 20% more than the dogs, I have at least that 44% advantage advertised for the TL.
Why not a flashlight? If you don't trust the terrain, you might need a flashlight (but try trusting the terrain - especially if it's a roadway). But for me, night vision is much superior. Flashlights create long pools of light that are limited in range and are usually very tunneling. And, of course, night vision is built it - so you won't forget to bring it along.