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#1
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Night Vision
I was just at the sportys website looking for one of those mini red LED
lights. One of the sidebars claims that, "These keychain flashlights emit a bright red beam or a bright white beam that illuminates well, yet does not affect night vision." I've been taught that white light destroys your night vision. Is this claim true? Joe |
#2
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AIM 8-1-6(b) contains information more recent than what you were taught.
Bob Gardner "Homer J. Simpson" wrote in message ... I was just at the sportys website looking for one of those mini red LED lights. One of the sidebars claims that, "These keychain flashlights emit a bright red beam or a bright white beam that illuminates well, yet does not affect night vision." I've been taught that white light destroys your night vision. Is this claim true? Joe |
#3
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"Homer J. Simpson" wrote in message ... I've been taught that white light destroys your night vision. Is this claim true? The major issue is INTENSITY. Keeping the light intensity down is the key. While given the same intensity, red will hinder your night vision less, you actually may bet away with dimmer illumination using another color. I actually find very dim white light to work fine. The back lighting on my Garmin 195 actually makes a quite suitable light to read the charts by. The military went with green because it interferes with their night vision hardware less, but some research points out your acuity is better with green light, meaning you can set it dimmer than you could with a red light. |
#4
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"Homer J. Simpson" wrote in message ... I was just at the sportys website looking for one of those mini red LED lights. One of the sidebars claims that, "These keychain flashlights emit a bright red beam or a bright white beam that illuminates well, yet does not affect night vision." I've been taught that white light destroys your night vision. Is this claim true? A 'bright red beam', will still hinder your night vision... The 'point' about red, is that (relative to other light colours), it can be used _slightly_ brighter, without destroying the adaption. However green is the colour that the dark adapted eye, is most sensitive to. So for a given 'amount' of light, green gives the best 'vision', but red damages the adaption least. 99% of red lights are still too bright. As an example of just how dim a light needs to be, think in terms of computer screen, dimmed as far as it will go, with the sides shielded (to catch the 'stray' light that tends to leak out the sides), and then covered with two sheets of dark red acetate. These keychain lights, work if shone through the fingers, and aimed away from the eyes. I think a lot of people who market this type of light, have no idea just how sensitive a properly dark adjusted eye can be. It is when you are standing outside at night, and see a cigarette being lit a mile away as an uncomfortably bright flash, and can see the ground details, and shadows from starlight (not Moonlight, which is bright enough to destroy good night vision), that you get an idea of the maximum sensitivity achievable... Best Wishes |
#5
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This is a good answer Ron..
Your eyes operate in the photopic mode in daylight (cone vision) and scotopic mode for night vision (rod vision). Your cones provide color vision and your rods provide monochrome vision. The peak sensitivity of photopic vision is right around 555nm (green), but scotopic vision has its peak sensitivity at around 580nm (yellow). The important thing is that the light level you use is low enough to avoid desensitizing your retina to dim exterior light in the real world. Exposure to light at too great of an intensity will consume rhodopsin and spoil your night vision. It can take up to 1/2 hour to become completely dark adapted. Since you rely primarily on your rods at night, red light does not hold any particular advantage because it affects your rods. In actuality, blue light might be a better choice because it will primarily excite your blue cones without affecting your rods as much... Another thing to keep in mind at night is the importance of using averted vision. Because your cones are concentrated in your fovea (center of vision) and you have very few rods there, you can't see dim objects if you look directly at them. Looking slightly away from them will take advantage of the higher rod density away from your fovea and allow you to see dim objects. You can try this by looking at dim stars in the night sky and you will see what I mean. Dean Wilkinson "Ron Natalie" wrote in message om... "Homer J. Simpson" wrote in message ... I've been taught that white light destroys your night vision. Is this claim true? The major issue is INTENSITY. Keeping the light intensity down is the key. While given the same intensity, red will hinder your night vision less, you actually may bet away with dimmer illumination using another color. I actually find very dim white light to work fine. The back lighting on my Garmin 195 actually makes a quite suitable light to read the charts by. The military went with green because it interferes with their night vision hardware less, but some research points out your acuity is better with green light, meaning you can set it dimmer than you could with a red light. |
#6
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What does taxiing with a landing light do to night vision? What about
flying over a city? Don |
#7
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Dean has some very good responses. I attended the "Into the Darkness: Unaided Night Vision" seminar at the November AOPA Convention in Philadelphia. Presenter was Andy Engle, OD, Captain, Medical Service Corp, US Navy, Refractive Surgery Clinic. An announcement was made at the beginning of the program, "If you do not intend to stay for the entire one-hour program, leave now. The doors will be closed and no entry or exit will be permited." All the door edges were taped and papered to seal out extraneous light. When the doors were closed, the lights were turned off. The presenter used a computer slideshow with colors and intensity selected so not to destroy the viewers dark vision. The first slide, he told us, was a photo of (something or other, I don't recall) on a black background. He told us not to worry if we didn't see it, we would be able to at the end of the program. I wish he had had a handout, the program was that good. As the program continued, and ones eyes adapted, one could actually begin to see the other people an objects in the room. At the end, the first slide was again shown and, indeed, the object he at told us would be there was faintly visible. This program was based on one that is given to Naval Aviators. |
#8
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Bob,
while we're at it, maybe a question from a friend: Consider a flight in night IMC. Why would there be any desire to keep the night vision good? There's nothing to see outside anyway, except for bright runway lights. Why not make the cockpit as bright as possible? -- Thomas Borchert (EDDH) |
#9
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Don Tuite wrote: What does taxiing with a landing light do to night vision? Nothing. What about flying over a city? Nothing. |
#10
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"Newps" wrote in message news:S0VKb.767486$Tr4.2204802@attbi_s03... Don Tuite wrote: What does taxiing with a landing light do to night vision? Nothing. Doesn't do anything for your night vision, but when you blast the other plane on the taxiway with your light it destroys his! About the only other outside-the-cockpit light that was problematic was when the tower turns up the Dulles runway lights into the penetrate the fog mode on a clear dark night. The normal illumination level is actually less than the lighting on the airport service road. |
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