Red light better for night vision - any difference in LED vs. incandescent?

I was talking to a friend about the light pollution in cars with screens and TFT dashes etc.

Then I was curious - red light is less harmful for night vision, correct?

Is there a difference if that red light is emitted by a diode vs. by a glowing filament? A difference in harm-to-ability-to-see-at-night?
Or is it all depending on the frequency of the light ("how red" it is)?


Secondary question;
Is there a problem with "light pollution" in cars? What with screens and bright LEDs and navigation and even instrument clusters being entirely made of screens now, I wonder if there's been a study showing that it affects our ability to see after being exposed to all that?

Lots of info and discussion in the "Night Vision" forum, including the thread stuck at the top ...

https://www.candlepowerforums.com/vb/showthread.php?18915-Human-Night-Vision-Preservation

Since I don't recall a recent Automotive-specific thread, we can let this one run here, thanks

ameli0rate said:

I was talking to a friend about the light pollution in cars with screens and TFT dashes etc.

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That causes problems, for sure. In the first place, any source of light within the driver's visual field degrades their visual acuity for driving. There is a common misconception about how glare works; people think up to a certain level it's "only" discomfort glare, then above that level it's disability glare. That's wrong -- it's the other way around: any light source within the driver's field creates some level of disability glare, and especially intense or luminant light sources create discomfort glare. Even yesterday's dim dashboard lights created some amount of disability glare (visual acuity degradation). Today's big, bright displays create a lot more of it.

They also create secondary safety issues in terms of encouraging improper use of the vehicle's exterior lights: dashboards are fully lit whenever the car is in use, so there's no longer any clue for the driver to switch on the full nighttime lights after dark. Hence, more vehicles running around with either no lights or only daytime running lights or, at best, DRLs and tail lights.

Then I was curious - red light is less harmful for night vision, correct?

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Yes, and blue light degrades night vision badly, and today's displays put out a lot of blue light.

Is there a difference if that red light is emitted by a diode vs. by a glowing filament? A difference in harm-to-ability-to-see-at-night? Or is it all depending on the frequency of the light

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Depends not on the type of light source, but on the spectral output of the light source (how much of what wavelengths).

Regarding blue light, you have to look at the spectral distribution to see how much blue wavelength the LED emits. In general, warmer color temps emits less blue wavelength versus cooler color temps. Also high CRI and R9 lights in general emits less blue wavelength because the thicker phosphor converts more of the base blue light into other wavelengths and allows less blue light to escape unconverted. The blue wavelengths that did not get converted through the phosphor are the "potentialy" health concerning portion of the light.


Here is a comparison of a 3109K vs 5678K led strip. Notice how the 3109K emits noticeably less blue light than the cooler 5678K.
https://www.aliexpress.com/item/32855114643.html?spm=a2g0s.9042311.0.0.27424c4dwi3jLY

Also I tested my SST-20 4000K 95CRI to emit a much smaller proportion of blue wavelengths than the 70CRI XP-L HI 4000K.

That's the reason why I like to use warm white lights at night. Notice, if your eyes get hit by a CW light of the same intensity as a WW light, you will be blinded for much longer with the CW light. I accidentally got blasted by the E21A 9080 2000K full output in my eyes and it didn't take too long for me to regain night vision. However, I remember similar intensity CW or even NW light hitting my eyes hurt much more and takes much longer for me to regain vision.

saab had a feature when all interior lights would go out only speedometer dimly lit. iirc it was on 9.5.

archimedes said:

Lots of info and discussion in the "Night Vision" forum, including the thread stuck at the top ...
https://www.candlepowerforums.com/vb/showthread.php?18915-Human-Night-Vision-Preservation
Since I don't recall a recent Automotive-specific thread, we can let this one run here, thanks

Click to expand...

It seems the links were dead in there, but the comments seem to indicate that red=good, other colors=bad.

-Virgil- said:

They also create secondary safety issues in terms of encouraging improper use of the vehicle's exterior lights: dashboards are fully lit whenever the car is in use, so there's no longer any clue for the driver to switch on the full nighttime lights after dark. Hence, more vehicles running around with either no lights or only daytime running lights or, at best, DRLs and tail lights.


Yes, and blue light degrades night vision badly, and today's displays put out a lot of blue light.

Depends not on the type of light source, but on the spectral output of the light source (how much of what wavelengths).

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1, I saw that a couple of times on a 7 hour drive. Several cars had the DRLs running and nothing on in the back. I'd think the easy part there is to just let your regular lights be DRL and have them all on all the time. Or automatic headlights. It sadly seems that we'd need a nanny buzzer telling you to turn on the lights otherwise.

2, Yes, the inside of modern cars is pretty annoying with that UFO-level flashy lights and buttons and screens. I did enjoy my 2006 Volvo with the gauges turn to the dimmest. Easy to see, yet not distracting. A warmish, dim glow of the LEDs is just what the doctor ordered. Of course, vis-a-vis the insane glare of Chevy trucks (why? don't Chevy have an aiming-the-damn-headlamps department for their new trucks?) or all the truckers with their Chinesium LED headlamp conversion, to the should-be-junked old cars with HID conversions and generally misaligned headlamps (on a lot of COMMERCIAL vehicles too!) maybe the instrument clusters aren't a big issue? The cynic/misanthrope in me can't wait for self-driving pods.

3, Thanks - so the source and its tech matters not, only the ångström of the light is crucial?
On a side note, when I worked at Coors Brewing Company, one of the engineers explained to me that the brown (and green, etc.) were to filter out a specific wavelength to prevent the sulfates to turn to sulfites in daylight and "cause the beer to taste like Corona", he added with mirth.

SKV89 said:

In general, warmer color temps emits less blue wavelength versus cooler color temps. Also high CRI and R9 lights in general emits less blue wavelength because the thicker phosphor converts more of the base blue light into other wavelengths and allows less blue light to escape without being converted.

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Warmer light being more red makes sense to me. Am I reading you right in that "high CRI = less blue"?

alpg88 said:

saab had a feature when all interior lights would go out only speedometer dimly lit. iirc it was on 9.5.

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I think a lot/most SAABs back in the day had it. The old 900 had it. I think they called it "stealth mode" or something, and it blacked out the entire dash save for the speedometer and tach. Neat, if a little gimmicky, though these days it wouldn't be THAT hard to make your clusters switch to mostly red or mostly off with speedo/tach/alerts being red.

The new Volvos are lots of bright white light from screens and buttons and stuff. It looks great during the day, but at night it feels more like an alien abduction scenario.

ameli0rate said:

It seems the links were dead in there, but the comments seem to indicate that red=good, other colors=bad.

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It's not quite that binary or simple. Minimal blue/violet content in the light is the main thing that makes for minimal degradation of dark-adaptation.

I'd think the easy part there is to just let your regular lights be DRL and have them all on all the time

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This is very wasteful and results in sub-optimal DRL safety performance. Headlamps just don't make very good DRLs.

Or automatic headlights

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This is the correct way to do it.

ameli0rate said:

Warmer light being more red makes sense to me. Am I reading you right in that "high CRI = less blue"?

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Yes. I edited my post above and placed an image for easier understanding. For more interesting reading about blue light in another flashlight forum, see this thread.

ameli0rate said:

1, I saw that a couple of times on a 7 hour drive. Several cars had the DRLs running and nothing on in the back.

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i drove my sonata several times like that without realizing, i always have the switch on auto, but when you give a car to either valet crew, or parking lot\garage attendant, they shut them off, when they return your car they do not tell you that, and you only realize it when you drive in a dark place, in the city however unless you look at dashboard and not see the indicator light that your lights are on, you wont know, cuz lights from light poles, store fronts, buildings, are so bright you would not see your lights even when they are on

My teardrop came equipped with a very bright light in the hatch that was at about eye level and shot its beam straight into your eyes. So I took it out and installed a few strips of white and a couple of red LEDs --- the red to soften the white. And I have one short strip of red to run as a "stealth" light to retain night vision while camping.
I hate light pollution in the woods. Prefer the glow of a warm fire.
The red is just enough to navigate to the fridge for a beer. Time lapse in the photo makes the red look brighter than it really is.
The mix of lights for cooking and whatnot.

Not to derail this thread, (here comes the but) but do you have anymore pics of that camper it looks aweful convenient, did you buy it like that or make some mods?

http://stlplaces.com/night_vision_red_myth/ provides an interesting read, perhaps a bit better than some links that an Internet search will find.

Given what I've read, including more-primary information, and that your eyes aren't going to be fully dark adapted (if they were, everything in your headlights would appear as monochrome, and you'd have a significant blind spot looking straight ahead), the lowest intensity that you can still read is probably the best setting. Yes, avoiding blues and UV probably helps.

I'd be careful about falling into the trap that thinking that the MIL specs for night-vison lighting are directly applicable (MIL-STD-3009 "Green A", "Green B", or the like) as those are intended to prevent problems with the night-vision system, not the human viewer.

Edit: The CP site now responding somewhat better than it was earlier, I apologize for repeating some of the information in the thread linked above.

Edit: I can't wait for the next trend in headlamps -- ultra-low color temperature -- which, of course, will be promoted as "Don't be a 'boy racer' with blue headlamps, get our rich, warm lights" followed by "because everyone knows that yellow ski goggles are used by the fastest downhill racers"

My new car has blue on the dash, which is the worst for acuity. I suppose they think green would make people go faster, and red cause anxiety. Or because blue is the popular glare ^h^h^h^h^h color...

dead link:
http://stlplaces.com/night_vision_red_myth/ provides an interesting read, perhaps a bit better than some links that an Internet search will find.

I very much despise all the light from modern instrument clusters and screens.
I can turn off the infotainment screen.

I actually removed the plastic bezel from around my instrument cluster screen and put window tint on it...then I reinstalled the bezel. It works great. At night, I can make it very dim (before the tint, the dimmest setting was still distracting). It has separate brightness settings for when the lights are off, so it's also very easy to see during the day.

It was possibly the best 30 minute mod I have done to my truck.

On modern cars I find myself doing the following:

• City driving: minimum setting +1
• Country driving: minimum setting

kingofwylietx said:

I actually removed the plastic bezel from around my instrument cluster screen and put window tint on it

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I have seen tint sheets sold for this purpose, maybe precut to fit.

I wonder if you can easily replace the lamps behind the dash panel, I would install green. Well, maybe not; I wonder what effect sunglasses would have on other colors.

I used universal window film from an automotive parts store and cut it to size once the bezel was out of the way.

I don't believe the dash lamps are replaceable in my vehicle.

I just completed a 2000 mile road trip in my old 2006 Volvo V70. I find myself dimming the cluster to just a hair over minimum at night and that lets me know my speed.

I also like that the car has no giant displays of any kind. Dimming the cluster also dims the soft green light around the buttons for climate control and radio.

This car also has a light sensor so when it senses daylight, it turns off all interior lights, regardless of headlight setting.

It'll be hard to replace this car with all the new ones having the 75" hi-def touch-screen neon day-glo Blade Runner settings on "high" all the time. Ugh.