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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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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) |
#4
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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 Until you break out unexpectedly. There's aluminum out there and it's not separated from you once you are out of the soup. Without good night vision you might not even notice you're now in 5 miles in haze over a layer. Jose -- (for Email, make the obvious changes in my address) |
#5
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Teacherjh,
Thanks, that's what I said, too: You'll still need to visually scan for traffic if it's anywhere near marginal VMC. And that's often the case. -- Thomas Borchert (EDDH) |
#6
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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. |
#7
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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. |
#8
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What does taxiing with a landing light do to night vision? What about
flying over a city? Don |
#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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