# What colors are best seen at night? **URL:** \ **Category:** Factual Questions\ **Created:** [October 21, 2015, 12:05am UTC](https://boards.straightdope.com/t/what-colors-are-best-seen-at-night/735304 "2015-10-21T00:05:23Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![Love\_Rhombus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/love_rhombus/32/10694_2.png) [@Love\_Rhombus](https://boards.straightdope.com/u/Love_Rhombus)\ **Post date:** [October 21, 2015, 12:05am UTC](https://boards.straightdope.com/t/what-colors-are-best-seen-at-night/735304/1 "2015-10-21T00:05:23Z")
If I were in a pitch-black cave and five people approached me with colored filters on their flashlights, is there a certain color I’d see the most easily? ---
**Author:** ![GaryM](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/garym/32/241_2.png) [@GaryM](https://boards.straightdope.com/u/GaryM)\ **Post date:** [October 21, 2015, 12:26am UTC](https://boards.straightdope.com/t/what-colors-are-best-seen-at-night/735304/2 "2015-10-21T00:26:58Z")
Green. Supposedly the human eye is most sensitive to green. Sorry, no cite. ---
**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\ **Post date:** [October 21, 2015, 12:52am UTC](https://boards.straightdope.com/t/what-colors-are-best-seen-at-night/735304/3 "2015-10-21T00:52:27Z")
There are two slightly different answers, depending on the brightness of the flashlights. If the lights are quite dim, then only the retina’s rod cells will be activated. These cells have a peak sensitivity at 498 nanometers, which is a sort of bluish-green. If the flashlights are bright, however, then the cone cells will play a part. There are three different peaks here: at 420 nm, 534 nm, and 564 nm. The two longer wavelengths actually overlap in their absorption spectra, and so I’d suggest targeting the midpoint: about 549 nm. This is more of a yellow-green. So **GaryM** is right that the answer is basically “green”, but the exact shade depends on the circumstances. I should note that I’m assuming a kind of laser-like narrowband color emission. A real flashlight (LED or otherwise) will have a broader spectrum. It may not be that lining up the spectral peaks actually gets you the maximum spectral overlap, though it should be fairly close. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [October 21, 2015, 1:10am UTC](https://boards.straightdope.com/t/what-colors-are-best-seen-at-night/735304/4 "2015-10-21T01:10:32Z")
Is it cheating to say that it’d be the white filter? ---
**Author:** ![septimus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/septimus/32/410_2.png) [@septimus](https://boards.straightdope.com/u/septimus)\ **Post date:** [October 21, 2015, 1:26am UTC](https://boards.straightdope.com/t/what-colors-are-best-seen-at-night/735304/5 "2015-10-21T01:26:47Z")
> [@Love\_Rhombus](#): > > … with colored filters on their flashlights… Filters block light without adding any, so I think **Chronos** ’ suggestion of “white filter” is clearly best. If you ask what color of laser would be best, given constant power, I assume those who suggested greenish colors are correct. ---
**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\ **Post date:** [October 21, 2015, 1:30am UTC](https://boards.straightdope.com/t/what-colors-are-best-seen-at-night/735304/6 "2015-10-21T01:30:50Z")
> [@Chronos](#): > > Is it cheating to say that it’d be the white filter? Maybe. But then I could say that if your flashlight is actually a 1064 nm laser, then a KDP frequency doubler makes for the best “filter”. ---
**Author:** ![Love\_Rhombus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/love_rhombus/32/10694_2.png) [@Love\_Rhombus](https://boards.straightdope.com/u/Love_Rhombus)\ **Post date:** [October 21, 2015, 1:49am UTC](https://boards.straightdope.com/t/what-colors-are-best-seen-at-night/735304/7 "2015-10-21T01:49:29Z")
> [@septimus](#): > > Filters block light without adding any, so I think **Chronos** ’ suggestion of “white filter” is clearly best. > > If you ask what color of laser would be best, given constant power, I assume those who suggested greenish colors are correct. Yeah, upon rereading I should have said “tinted covers” or somesuch. ---
**Author:** ![Your\_Great\_Darsh\_Face](https://avatars.discourse-cdn.com/v4/letter/y/ac8455/32.png) [@Your\_Great\_Darsh\_Face](https://boards.straightdope.com/u/Your_Great_Darsh_Face)\ **Post date:** [October 21, 2015, 5:40am UTC](https://boards.straightdope.com/t/what-colors-are-best-seen-at-night/735304/8 "2015-10-21T05:40:45Z")
No odds. A “tinted cover” is still a filter - if it turns the light pure red then it has blocked the approximately two-thirds of the light that was blue or green, so the overall brightness has gone down. Even if it turns the light “reddish” it’s not done that by adding more red but by removing some of the non-red. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [October 21, 2015, 12:38pm UTC](https://boards.straightdope.com/t/what-colors-are-best-seen-at-night/735304/9 "2015-10-21T12:38:20Z")
Said another way, it depends on whether their flashlights were measured to have the same total brightness before or after the filter was applied. ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [October 21, 2015, 1:53pm UTC](https://boards.straightdope.com/t/what-colors-are-best-seen-at-night/735304/10 "2015-10-21T13:53:23Z")
Lighthouses use white light. That should tell you something. It also tells you that the best “filter” is a temporal filter, i.e. modulating the brightness over time. So really, the best filter is a black filter that you install and remove every few seconds.