Red map light: good idea?

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eggsalad

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A long, long time ago, it was commonly thought that red light would do the least short-term damage to night vision. Folks at Pontiac and BMW and others used red lighting for their gauges, presumably for this reason.

I wonder if that's still common wisdom and/or fact.

My '08 Prius has a pair of overhead "map lights", using T10/192/168 bulbs. I have the idea of converting one of them to red LED, so if I wanted to look for something at night, it would be less bad for my night vision than the current "cool white" LED map light.

Is this a good idea, or am I working with outdated information?
 

zespectre

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I replaced the map lights in my Volt with red LED. I couldn't say if the end result is due to the red, or them being somewhat dimmer than the white bulbs, but now if my wife flips on that light without warning (as is her habit) it certainly has less impact on my visibility as the driver.
 

Alaric Darconville

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A long, long time ago, it was commonly thought that red light would do the least short-term damage to night vision. Folks at Pontiac and BMW and others used red lighting for their gauges, presumably for this reason.
Or to "look cool" and with the (hopefully unintended) effect of helping to mask dashboard warning lights.

Replacing the lights with *not too intense* red would help preserve night vision. Even too-intense red light damages night vision. Some of the red LED ones may be too intense.

Red light will make maps with red markings harder to read, though.

In my '01 Corolla, the little map lights in the rear view mirror have been replaced with 194A ('amber') bulbs which are slightly less troublesome than white light. Is it the removal of a lot of blue light, or just the reduction in intensity? One could guess either way, or even that it is the intersection of reduced blue light/reduced light overall.
 

StarHalo

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The only way red light doesn't affect night vision is if it's so dim that you can't tell it's red; 660nm+ and moonlight mode only, most "red" LEDs are ~630nm, and the interior light of your car is certainly not moonlight. You have zero color recognition using a single-color light for a task anyway.
 

HKGuns

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It is 100% fact. Subs rig for red before going to periscope depth for this reason. Pretty much a well established fact in the military circles.
 

-Virgil-

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Difficult to read/see stuff under red light. You can reduce dark-adaptation damage by attenuating the blue without going all the way to red; put in these (or if you want to experiment with red anyway, use these.)
 

HughJorgan

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Once upon a time I switched my car's map lights to red bulbs. I left it like that for years but really it wasn't a good idea. Reading maps or general purpose, it's just too hard to see details. Blue lights are recommended for nighttime reading of maps specifically, they don't impact your night vision as much while also don't wash out markings on the maps. But I doubt these days you use your car's map lights to actually read maps. For a softer general purpose use, I like Virgil's recommendation of an amber light.
 

-Virgil-

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"Blue lights are recommended"...by who? Blue is not a good choice for nighttime seeing. It has the largest negative impact on your dark adaptation.
 

JoeGill

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We have two types of photoreceptors in our eyes: rods and cones. Cones come in three basic types: mostly red-sensitive, mostly green-sensitive and mostly blue-sensitive. (That's why we have Red-Green-Blue, RGB, monitors and TVs. Combining these three colors at different intensities is perceived as different colors of light.) Rods are 100 times more sensitive to light, but don't register color. Both rods and cones become desensitized in bright light, and in dim light--if they have not been desensitized--only the rods are sensitive enough to work. One of the several proteins involved in vision--rhodopsin--in rods is not sensitive to red light. So, we can use bright red light that is perceived by the red cones to illuminate things reasonably well without desensitizing the red-insensitive rods we need to see in very dim light. In other words, red light helps preserve night vision (the ability to see in very dim light) because it doesn't desensitize rods the way higher-frequency colors of light do.

Using a red map light lets you use lots of light to read the map, then use very little light to hike the trail, see the road or stumble to the bathroom.

By the way, I am a Scoutmaster, and I encourage my Scouts to use the dimmest possible setting on their flashlights, and to be careful not to shine them in the eyes of fellow night-walkers. People are often surprised at how well they can see if they let their eyes adjust to the darkness, how quickly they can lose night vision with a burst of bright light (including the reflection of high-beam flashlights off trees or buildings or fellow campers), and how long it takes to recover. It takes five minutes to recover the majority of night vision, and almost an hour to fully recover it. When we are stargazing, I use a dim red light, and have people notice the difference in how bright the stars seem when we start, after five minutes, and after 20 minutes. Some people never see many stars, because they never let their eyes adjust enough to let the starlight register.

If you have ever woken in the middle of the night to go to the bathroom, you may have noticed how much brighter the path seems than when you went to bed. That's because the proteins responsible for night vision have had a chance to return to full working order.

Hope this helps!

Joe Gill
 

HughJorgan

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"Blue lights are recommended"...by who? Blue is not a good choice for nighttime seeing. It has the largest negative impact on your dark adaptation.

I wasn't saying blue was a recommended nighttime light. I said it was for nighttime reading of maps because the color doesn't wash out markings (compared to red or other colors).

Back when I got my SRT9, it had red, green, blue, and UV modes. I was well familiar with the uses of red and UV and I'd heard about using blue to see blood trails but I wasn't sure what the practical purpose was for green. In researching it, using blue for maps was one of the other factoids I gathered. Here's one reference a quick google search comes up with; there are others:

http://www.flashlightuniversity.com/led-colors-and-uses/
 

-Virgil-

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In researching it, using blue for maps was one of the other factoids I gathered. Here's one reference a quick google search comes up with; there are others:

http://www.flashlightuniversity.com/led-colors-and-uses/

You appear to have made a very common error: mistaking a web search for "research". That site you just linked has this little gem: Blue light is the only light that can cut through fog, which is why it is widely used for fog headlights.

Ummmmm...no, blue isn't the only light that can cut through fog, because because no it doesn't; there's no light that can "cut through fog". And no, blue is not used widely (or at all) for "fog headlights" (or any other legitimate vehicle lights except the flashing ones on police cars).

Just because it's on the internet doesn't mean it's true -- not even if it's on a site claiming to be educational.
 

Sadden

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I swapped out the cab lights in my big truck for red. I find it much more comfortable if the swamper needs too grab something while i am driving. Plus it looks cool.

The peterbilt has a floodlight on each side as well as an aimable spotlamp. I swapped the floodlight out for red and left the spotlight clear so i have an untinted light for doing paperwork/logbooks.
 

Alaric Darconville

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Once upon a time I switched my car's map lights to red bulbs. I left it like that for years but really it wasn't a good idea. Reading maps or general purpose, it's just too hard to see details. Blue lights are recommended for nighttime reading of maps specifically, they don't impact your night vision as much while also don't wash out markings on the maps.
If the map has any blue marking on it at all, they'll be invisible under blue.

Blue is also a TERRIBLE light color if you intend to preserve your night vision.
 

-Virgil-

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I would be reluctant to have only red cabin lighting in my vehicle. It seems to me that could make a police officer "hinky" if they stopped me after dark.
 

lightfooted

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I thought green had become the preferred low light color for reading paper maps as it doesn't make the red warning and danger markers disappear nor does it make it difficult to see bodies of water, two rather important things you need to see when using a map on a rally course or S&R run. Personally I'd rather just use a low intensity white light for map reading.

That said, my 2001 VW Passat has a pair of red LEDs mounted in the rear view mirror pointing down to illuminate the console area for seeing the controls, it works fine. It also has red led back-lighting for all the window and lock controls.
 

zespectre

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so this got me curious. I had an amber LED handy so I pulled one of the red map lights and made it amber.
well what do you know.... I like it

I think I'm going to switch them both to amber (though I'm leaving the DOME lights alone.
 

-Virgil-

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We're days away from the year 2018. Are we really still trying to read paper maps in the car?
 

eggsalad

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We're days away from the year 2018. Are we really still trying to read paper maps in the car?


I'm not, nor was that the intention. But I do "store" random items on my passenger seat, and sometimes I need to locate one of them when it's dark.

The dome light will remain cool blue/white, as will the driver side map light. Only the passenger side will be changed to red. If I don't like that, I'll try amber. They're cheap enough to play with.
 

Bicycleflyer

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We're days away from the year 2018. Are we really still trying to read paper maps in the car?

Yes, I still carry paper maps. I even use them. Heck, I even have phone books and a city directory. Technology does fall short sometimes. My GPS does create goofy routes sometimes and my smart phone has failed to load data.

As for the red light, I have flown airplanes that use a red flood light. In those instances I have had to use a flashlight at times to see what the red has washed out. VFR charts use a color called magenta, which is a reddish color. That washes out all the time. Truth is, most newer planes just use white light.

Green is used by the military during NVG flights to prevent the red from glaring in the googles.

As I understand it, red does not affect the eye's acuity. Perhaps that is the reason it is used on gauges.
 
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