Why Are Streetlights Turning Purple? In Depth Analysis and Fix

[@nasenbaer4627]

I don't know why KZbin decided to seemingly randomly recommend this video to me, but I'm glad it did.

[@lokiva8540]

I follow a variety of civil and electrical engineer hosted channels, and make comments as an older engineer, and so that's easier to guess in my case.

[@mikebergman1817]

Same lol. I am appreciative though.

[@WackoMcGoose]

@@lokiva8540 Almost certainly significant overlap with Road Guy Rob, Practical Engineering, etc...

[@Leopoldo888]

I was watching videos about Space X's problems and also visits to Macchu Picchu, Perú... no relation at all but was a very good discovery.

[@lokiva8540]

@@Leopoldo888 But it was Bezos whose space flight generated multiple petitions to help turn his ticket to one way only.... Elon is crazy, but not that malicious to so many victims as Bezos and his gang.

[@yucannthahvitt]

Given how expensive these lamps are, I’m surprised there haven’t been lawsuits against the suppliers. LEDs are consistently advertised as long lasting and these things are failing faster than the bulbs they replaced

[@YourBonesInMyDresser]

Aw who cares! Taxpayer money!!!!!

[@joej3365]

No, they aren’t failing as fast but yea they definitely are made cheaply. Light Emitting Diodes definitely last longer. It’s an issue with the coating, the led works fine.

[@captainobvious8665]

​@joej3365 Everyone I've spoke with about the topic of consumer grade led's has had the same issue: They last nowhere near as long as an incandescent or cfl. What is happenning?

[@VEC7ORlt]

@@captainobvious8665 what are you talking about? Less than incandescent? At 1 or 2k hours? With LEDs lastin years and years.

[@Validole]

​@@captainobvious8665the cheapest of them usually come with severely underrated (as in, rated too low for what they're used for) rectifying and current control circuits. Those are what will fail.

[@Rayzer2368]

As a truck driver driving all over the country I have seen this many many times. I just figured it was some new weird push to reduce light pollution. Thank God that’s not the case and they are fixing/replacing them!

[@fastonfeat]

As an amateur astronomy nerd, I would like to reduce light pollution. I do NOT want taxes spent on 'initiatives', loss of driving safety, or HOA Karens! Seems an easy fix with bonnets/shades. I find the lights diminish visibility when they are directed at my eyes (looking at u drivers, leaving your brights on).

[@sergpie]

@@fastonfeat Im not sure why, in 2024, proximity sensor-equipped light posts and/or ambient brightness sensor to adjust emittance accordingly, aren’t a thing.

[@daliasprints9798]

It's making light pollution worse, not less.

[@sbdpro2]

Actually you could decrease light pollution with blue light. Because our eyes are way more sensible to blue than to yellow light, it would be possible do decrease the light amount and power producing it with the same brightness for our eyes.

[@daliasprints9798]

@@sbdpro2 Light pollution is not a matter of the raw amount of light energy but its effects on human and other biological systems. Blue light is much more harmful in that regard.

[@MrTechnicks]

Industry expert here. These are caused by a problematic LED manufactured by Seoul Semiconductor. This issue is well known in the industry. It has something to do with the phosphor delaminating from the die if I remember right. They have been paying for replacements for years now.

[@POTATOEMPN]

Delamination indeed.

[@heyitsdrew]

why does it seem like the second they replaced the light it is this color? if it deaminated did that happen immediately?

[@lok777]

@@heyitsdrew The lights on my street took a few months before all turned purple. They were replaced but are turning purple one by one all over again.

[@cat_say_hey]

Sounds like they need TSMC

[@psalmtt8784]

@@lok777 If you believe this video or the "malfunction" lie... smh

[@deusexaethera]

As a lighting enthusiast, I'll give you the TL;DR: White LEDs are actually blue LEDs with phosphor coatings that convert some of the blue light into other colors. Those phosphors degrade when overheated.

[@noxious_nights]

I wonder if this means these street lights go purple more in hotter regions.

[@michfis7]

Thank you! Gosh these long videos that should have just been one sentence!

[@falxonPSN]

Or in this case when incorrectly manufactured or if a poor phosphor type is chosen.

[@MrGencyExit64]

"Lighting enthusiast," now I've heard it all :)

[@fgjewbjlvwgl]

@@noxious_nights Not necessarily. Improper cooling, heat buildup when under operation is the main reason.

[@CA_Don1181]

I have a friend who heads the city in bidding out these lights, and other municipal equipment as well. I noticed our streets were tuning purple and asked what was going on years ago. He said exactly what you said. The degradation of the phosphor coating is causing the light not to be filtered properly. He knew this was going to happen based on research, but was required to take the lowest bidder due to policy. Now they are playing whack a mole as all the lights go purple. He said if they would have went with the proper manufacture, the city would have saved 100's of thousands of dollars, if not millions.

[@mark7362]

We really do live in idiocracy... It is comical that they still just keep on installing them knowing they're messed up & they'll be blue/purple. Jokes about a person having difficulty changing a lightbulb used to be jokes, now it's reality 😂 make America great again 🇺🇸

[@NarcFreedom]

And the dollars “saved” in energy is probably negligible or nonexistent now. The spent millions to save pennies.

[@rogerwilco2]

In Europe you can structure your bidding process in such a way that you avoid having to go for the lowest bidder. It requires a bit more work to write the bidding documents and some thinking about tests to determine quality.

[@boomergames8094]

@@rogerwilco2 We don't have to use lowest bidder simply based on "price". We write 'specifications' and a "cost" measured in years, such as "12-year total cost including labor and replacements". I've worked with many bids for large organizations. Price vs. Cost. Its a lot more complex wording and legaleze... :) My question is "did the manufacturer KNOW that these would have issues and need replacement, and at what timeframe?"

[@ChrisChocol]

so, that guy didn't do his job correctly, if he knew ahead of time. or more likely corruption forces his hand example of somebody getting paid to play most likely.

[@danlowe8684]

As far as I know (contractor that has worked in the biz for 35 years), it is only one manufacturer that has this issue, and it is American Electric Lighting (AEL), a subsidiary of Acuity. They carry a 10-year warranty to the owner from date of installation. One issue with the warranty is that the owner must provide the lane control, labor, and equipment to make the changeout of the defective unit. The units cost about $300/ea. for the common 'cobra head' style in the video.

[@yo_marc]

This is the post I was looking for… I have never seen a purple light and don’t recognize those housings.

[@ocieward]

I’m genuinely surprised the cost of the lamp head is only $300. That’s significantly less than I expected

[@danlowe8684]

@@ocieward And, given the inflation of the past few years, they may price out at $350, now. But the whole problem is that municipalities bought into the LED program given the $20 cost of an HPS light bulb's 3-year life span, vs. the $800 LED light fixture cost, with 5-year warranty. Once they went 10 years on the warranty, and dropped the price, it made sense to switch, given the labor, equipment, and traffic control expenses involved. Now, the problems with production likely didn't surface until well into this warranty period. And this is where we stand, today - with a bunch of bad products, still under warranty.

[@jpdemer5]

The cost of the lamps is a small fraction of the cost of replacing them.

[@TheMW2informer]

There’s nothing wrong with the LED it’s just a film that failed, plus the blue / purple light looks a lot cooler and makes things like deer stand out easier.

[@random_n]

Thermal expansion causing delamination of the phosphor? Definitely. Here in the Canadian prairies where it gets down to -20C for weeks, the bad lamps have had something like a 1 year service life. I've driven down entire major roads lit like a Glow Bowling alley. Even better when it gets below -30C and they start strobing too. I'm all for efficiency, but these have just not been fit for purpose. I'm not surprised that they're junk due to an obvious engineering oversight with a trivial cheap fix, but I am surprised that the municipality still keeps buying them.

[@NanoPalomaki]

Interesting! 1 year is crazy. Here in the lower 48 it seems to be 3-5 years. I think with the new design this won’t happen again.

[@pileofstuff]

The lowest bidder strikes again!

[@VEC7ORlt]

Its not thermal expansion, it most likely moisture ingress and cheap LEDs.

[@threeparots1]

Calgary hasn’t been too bad. Only one section of highway that is quite noticeable..most of the city’s light have been quite good and reliable even at -30c. I have noted a few more light strobing which is more of a driver issue, which also shouldn’t happen. Faulty temperature sensitive components. Some weirdos saying it’s a 5G thing…

[@pileofstuff]

@@threeparots1 Winnipeg has entire streets that have gone blue.

[@elonmask50]

Interesting video, as an Aussie, I have never seen this issue here, which is really lucky because that blue light would really confuse the Kaolas. Our LED Road lights, usually go all Disco Duck, due too capacitor failures in the switchmode power supplies. I'm really glad that the algorithm decided that I needed to see your video.

[@WadeMcLure]

I was literally just talking about this the other day after noticing half the lights at a local car dealership were purple/blue... Of course now this is a recommended video, Big Brother is always listening!

[@seinfan9]

Same here. Bastard Brother, really.

[@red9350]

Finally an explanation!! It has been bugging me for a whole YEAR!

[@ethansmith9065]

My kids will look back on purple street lights the same way I look back on the orange street lights.

[@RegularAssUsername]

A few seconds on Google could have solved that riddle.

[@shawnkelley3695]

...KZbin!

[@BikiniDuckCreations]

This all started right after Prince died. The first purple street lights were in Minnesota. It is his ghost haunting the system.

[@djmips]

That's too funny, we started singing - Purple light, purple light only want to see you bathing In the purple light

[@BangBangBang.]

you can hear the guitar playing too

[@lokiva8540]

That's a Garbage claim. I'm only happy when it rains. Purple Rain, purple rain?

[@HughJanus-o3e]

Prince only Haunts the Rain with Purple.

[@alexpacura9810]

Rip prince and Joan rivers both died for the truth

[@richfiles]

Honestly, the whole transition to these bright white LED street lamps has been a curse for light pollution. If I were replacing street lamps, I'd say we should try to be using yellow LEDs with a wavelength close to Sodium lamps. You'd retain better night vision when passing into and out of the lamp's illumination, and it would cause less disturbance to wildlife. You could _still_ use a small number of white LEDs in the lamp to help improve color rendering, but not so many as to be overpowering. Yellow LEDs do not rely on a phosphor to produce their light.

[@mike_w-tw6jd]

lower color temperature - yes, monochromatic - no

[@jay-em]

It's counter-intuitive, but even though generating white light is less efficient, humans see white better than yellow, so lux levels can be lower (we evolved to see in moonlight).

[@JamesRandall1]

He did mention this in video but not as succinctly as you. Appreciate you pointing out that the intuitive assessment isn’t correct.

[@Torbjorn.Lindgren]

No, we now know that's a bad idea! The reason for this is that we now know that the eye is fairly insensitive to sodium yellow under mesopic vision circumstances - which is what happens when used as street lights and people had missed this for a long, long time! Yes, it's does work fairly well at daylight levels but as a STREET LIGHT at a fraction of this it's *bad*, unfortunately the human eye is very analog and didn't behave like they assumed. IIRC low-pressure sodium light gives roughly 1/4 of the "usable illumination" that people used to think it did - basically it's almost as bad as that purple light. This is a great part of why modern street lights changed to a wider and more whiteish spectrum - at the same lumen level we now know that for the human eye it works far better for street lights than the same amount of light in sodium yellow (whether from sodium or LED), this far outweights the efficiency of LPS streetlights that old designers were misled by. Basically, narrow-band illumination for street lighting in general is a bad idea except when absolutely required (IE near a visible light observatorium).

[@SIBUK]

I wish they would do this as well. I miss the yellow sodium lights. They could maybe make them the colour of the high pressure sodium lamps. They had more white in but they still had a really pleasant cosy colour to them.

[@Vandebirt]

I know most people don’t like the hue these lights emit but for some reason I find them pretty calm and gives the city a very futuristic/modern look at night. I wholeheartedly love them.

[@Curious-Mr.-Lee]

They are destroying everyone's eyes, but I it's such a cool effect. Reminds me of OG Sci Fi movies

[@whatsup7535]

It does. It makes everything look prettier and they are also soothing.

[@halutena736]

They're not doing damage to anyone's eyes. Do you also think our water has poison in it? ​@@Curious-Mr.-Lee

[@davidslaton]

Agree 100%!

[@TheMW2informer]

Yesss someone else who gets it!! Wish some cities would roll with it and maybe install some other colors down their Main Street.

[@LawyerPanda]

I live near an entire parking lot of these purple LED street lights - like literally every single light on that one property. I honestly thought the developer purposefully chose that color tone for some legitimate reason. Thanks to this video, I'm tempted to conclude the developers didn't do their careful research, or they just cheaped out.

[@lwilton]

Being old, I had to chuckle at your comment of "the white light we are all used to". When I was young, streetlights were mercury vapor lights, and were basically monochromatic blue, though not as deep blue as the failed LEDs. Later this was replaced with sodium vapor, which is just as monochromatic as you can get, as well as being stupendously ugly. It's only been the last few years that the world has returned to the concept that outside lighting can be polychromatic.

[@jsteezy80]

I was born in 80 and all I remember is the amber street lights growing up myself

[@jouniko]

One mercury vapor light between a row of high pressure sodium lights looks like an oasis to me.

[@AnnaVannieuwenhuyse]

@@jouniko It's also pretty remarkable how different a HPS bulb looks when it has failed. The soft glow from the heater inside causing a small amount of excitation, but no arc.

[@gorak9000]

mercury vapor isn't that monochromatic - sure it has a blue tint to it, but it's not like a blue LED. Same thing with sodium - only the low pressure sodium lamps are truly monochromatic - the high pressure sodium is more polychromatic, but still predominantly orange. Being born in the early 80's, I definitely remember the switch from mercury vapor to high pressure sodium lights. The whole city I grew up in was originally mercury vapor, and then they swithced all of the streetlights to high pressure sodium within a year

[@1marcelfilms]

One sports gym around here is lit by half mercury vapor lamps half HPS lamps. Its super damn ugly.

[@zashbot]

Honestly I thought the blue color was some sort of anti homeless measure

[@seands650]

That's exactly what I thought too, like maybe the light was uncomfortable or irritating to be around for too long

[@aenetanthony]

@@zeecampbell7754That seems odd, I can’t see how poorer light quality would improve suicide prevention outcomes. Is it something indirect, like blue light at night increasing happiness or something? Seems odd

[@bluecollarmage4512]

I thought it was drug addiction aversion. Can't see a vein that way. Ever been to a disturbingly blue bathroom?

[@jenbanim]

There are so many legitimate reasons to be upset with the government, please don't jump to conclusions like this because you're just taking away attention from actual problems that need to be solved

[@a_trauma_llama2991]

We're not? Considering in my city the lights are MOSTLY in areas that are dense, thus higher homeless. Given our already learned experience with blue lights in bathrooms as an anti-drug use measure, it's not illogical. You're right about the Sx prevention pondering in that it makes less sense, but there's been a lot of awareness around overdoses and deaths and mental health, its easy to see it come together when no other answer seems more plausible. I've also seen them at large intersections that were recently renovated, so I wondered if they were some poorly marketed "better visual quality" trial. I'm so glad for niche deep dives on KZbin answering my night drive questions!

[@notpc48]

The phosphor is reacting to the large amount of UV. When it is "broken" it actually makes a great BLACKLIGHT! I discovered this one night when working in the area. All my HI-VIS safety clothes were glowing brightly. 😎

[@100pyatt]

Very very bad for your eyes

[@GOPRepubliklan]

@@100pyatt Who cares? Looks cool AF.

[@featherdabirb]

@@100pyattit’s bad? Potentially yes,Do we care? No it’s fun for short periods let em enjoy it

[@featherdabirb]

@@GOPRepubliklanexactly!

[@VEC7ORlt]

@@notpc48 there is literally zero UV in that light.

[@davidslaton]

I’m in Orlando and noticed this along the highways and love it. I wish they were all blue or black light colored, makes it feel like I’m driving in TRON!

[@XerxezsX]

This explains every time I get to the freeway there's a purple lamp, looks cool.

[@stevenickolls8016]

Before they replace damaged purple lights with new white (that emit large amounts of blue light that affects wildlife and human sleep) are there better colours, I recall redder lights are less damaging to nature while preserving vision at night.

[@Torbjorn.Lindgren]

The original color of the street lights are likely optimized to give the best perceptual vision for the given amount of power (because power is the major cost) under "mesopic vision" (low light, but far more than moonlight) that street lights usually operate under, the eye behaves differently than at higher light levels (and lower!). Red or yellow light works great at DAYLIGHT levels, but not under the light levels street lights are normally operated under, this is something we've only known for a decade or two - hence why LPS (low-pressure sodium) used to be so popular but isn't any longer, despite still rivaling LEDs on lument/watt - you get a lot more usable vision with the same number of lumens & watts with whiter broad-spectrum street lights. You could crank up the illumnation a lot to compensate, but then the higher light level likely makes it worse for the wildlife anyway. So getting the "fixed" light to end up somewhere in the ballpark of the original spectrum is the easiest way to get close to the "proper" amount of light, substantially shifting the colors will likely mean they need put up extra lights to hit the required visibility. Oops.

[@MathewMoss-fp9ju]

Realistically we should use less aggressive light frequencies like green or red or like the UK had in the past old sodium vapour orange yellow lamps which made everything look a yellowish grey monochromatic appearance

[@markwhelan1652]

The military is actually going to blue lights on ship bridges at night as it works better than red.

[@TexasStormChaser]

What happens when you use the cheapest chinese LEDs you could humanly source. Those lamps probably cost $20 to make, and they charge the city $1500 each.

[@c31979839]

These are Universal Lighting LED/boards. The LEDs for these chip boards were not Chinese sourced.

[@thom1218]

@@c31979839 That's factually incorrect.

[@NosebergEatzbugsVonShekelstein]

The joys of being a criminally incompetent chinky-boo.

[@nyetloki]

That's why they are supposed to have a great warranty and guaranteed specs.

[@markconley9279]

I bought inexpensive 8’ led strip lights and after a couple of years they’re losing leds one by one.

[@mikes9939]

There's a shopping center in Smyrna, Ga with a Publix store in it that has these defective lights in the entire parking lot. I thought it was some kind of new type of light but am glad to know that it signals a big group of bad ones. Let's just see how long it takes the property management company to do something about it. These lights how very poor lighting and it makes the entire parking lot unsafe. Thanks for this video, always great to get some good knowledge about problems like this.

[@michaela6147]

Your safety is up to you. No one else

[@SleepingComputerEXE]

Thankfully, my city seemingly avoided the bad batches of LED streetlights that are turning purple. Though, I've seen my fair share of other failures with the streetlights (not starting, lights flickering/flashing, photocell modules seemingly failing(?) on some streetlights leaving entire blocks unlit).

[@rmp5s]

Yup...I'm in Phoenix too and a bunch of lights around the corner from my house did this. I looked into it years ago and found out it was a failure and WASN'T intentional. Cool to see inside what's actually happening.

[@Graymenn]

have they been replaced?

[@rmp5s]

@Graymenn Not sure, actually...don't go over there often. I doubt it. 🤣

[@therealchayd]

I remember this happening on our neighbor's LG TV backlight. Quite an interesting repair when you've got a massive thin sheet of LCD glass that you have to remove without breaking it.

[@harrysmbdgs]

I was about to say this is also a common issue with cheap LG TV backlights!

[@ratei]

We have this on our LG 42" 4K TV2017 for around $500. After 2 yrs of use, most part of the backlight turn purplish. Very disappointing.

[@HectorFabela-k6u]

I am a contractor and I replace the LG TVs all the time in hospitals and Doctor Offices. I just report the TV as Smurfed and install a new one. Maybe other brands do this but every single one I have had to replace was an LG.

[@harrysmbdgs]

@@HectorFabela-k6u Smurfed 😂😂 That’s brilliant, weirdly similar to what I told people - that their options were either to replace the TV or use it as a dedicated Smurfs TV from now on 😂

[@tartanele5984]

I still have this problem.

[@thegreyfuzz]

Interesting.. they just replaced a a mile long stretch of interstate lights near us with LEDs... they are all the blue color and have been from day one. Wonder if they are just not doing the coating to render white light or this was another great product filled with Chinesium.

[@patrickwright8552]

Excellent. Rtings' burn in test has TVs doing the same (your local Best Buy may as well, particularly in 43", 60", and 70").

[@danielbrendemuehl7841]

About four Winters ago the summer before they had just replaced a bunch of street lights in town with LEDs and it got so cold that winter that several of them turned purple and I tried looking for why this was happening and didn't find anything. I am very grateful someone is finally addressed this

[@davida1hiwaaynet]

Thanks for this info. The general store I go to has parking lot lights which have turned deep purple in this manner. I had always assumed the phosphor had somehow broken down or "burned" but it's interesting to see that it just chipped off.

[@blargcoster]

Before watching the vid, I had the thought that blue light makes you less sleepy. Always hearing the whole blue light from phones and monitors cause you to stay awake longer or not be able to sleep.

[@PsRohrbaugh]

That's an unintended side effect for animals, and people who have street lights that shine into their houses (I use my yellow street light as a nightlight). For drivers, it provided much less usable light, and ruins your vision making it very dangerous if you transition to a rural road with no streetlights.

[@mrrooter601]

imagine if we went back to light that was low enough your eyes could actually adjust and stop trying to turn night to day.

[@mickwolf1077]

I miss the high pressure sodium Street lights. I didn't know you could get that phosphor stuff either.

[@fritzmiller9792]

Metal Halide was superior to High Pressure Sodium for light quality and longevity. Regardless, both of those lights are ancient history now that LED lights have become more affordable.

[@mikafoxx2717]

​@@fritzmiller9792 Perhaps, but less so for efficiency. Also I liked that they didn't cause melatonin to go away - maybe not the best thing while driving but for walking or being near the lights, windows etc.

[@j7ndominica051]

Not ancient yet. Sodium lights are still in use.

[@GOPRepubliklan]

@@fritzmiller9792 Metal halide suffers from cold restarts. HPS doesn't.

[@fritzmiller9792]

@@GOPRepubliklan HPS fades, the guys I know in the local utility company told me they regret ever installing them. They were marketed as a longer lasting light but that was not the case and the light is truly horrible. Overall, a giant fail. Same with T-5 vs T-8....T-5 cost much more and failed at much higher rate. I refitted a large factory with them and learned it the hard way.

[@sparkythebuilder]

Thanks for this video. I recently noticed all the lights on a grocery store near me were purple. This video explains why.

[@johnhaller5851]

The Costco near me had all their lights turning to strobes, as they replaced them one at a time as they failed.

[@vallietmc9553]

It would seem to be the heat index causing the fail?

[@btag256]

Finally an explanation for those night club colored street lights! I thought it was some new thing to try and keep drivers awake with alternating blue lights on the highway.

[@mlies37]

Not just across the country, across the world! This has been happening over here in my little Dutch town as well. I’ve been wondering about this so it’s great to finally know why! Also kind of a relief it’s not throwing a bunch of UV at me, I was a little concerned about that.

[@njdotson]

I like the thought that they would accidentally get UV lights and give everyone a few more lifetimes of radiation

[@cle4tle]

@@njdotson you get plenty of uv outside during daytime

[@psirvent8]

@@njdotson Purple light like you see in this video is actually pretty close to the longest UV wavelengths, UVA, which goes from 315 to 400 nanometers. It can make things glow and also cure some resins as well. Some party blacklights are UV while other are only near-UV pretty much like the bad LED's shown here. Both can mess with your eyes and skin so it's probably a good idea not to get too much exposure to either of those.

[@fintux]

I've never seen these. I've seen some flickering ones, but not ones turning blue (I live in Finland). At least in my home town, they tested dozens of types of LED lights in different street segments to evaluate in real world conditions which models to use eventually, so even if that meant delayed adoption of LEDs, I guess that experimentation actually paid off.

[@DarkAttack14]

You'll be alright lol. The high pressure sodium lights my apartment building uses in the parking lot throw off an insane amount of non visible light. If you walk far enough away that you don't actually notice any of the visible light and look around with a phone camera everything shows up vibrant green. First noticed it taking a video of my dog on a walk, from around 400 feet away she was glowing green like an alien dog of some sort haha

[@JeffBezosVEVO]

Always assumed these purple lights were fixtures being installed to deter addicts as they make it quite difficult to see your own veins under these lights, and have seen many in places that would make sense in this context, very interesting to learn that it is actually a manufacturing defect and not a deliberate act.

[@T8ersalad]

I have worked in the addiction recovery industry and some of the addicts would use an ink pen while in good lighting to mark the placement of their vein so they can successfully inject even if there’s poor visibility. I rolled my eyes and thought it was the stupidest thing. It’s like walking around screaming LOOK AT MY IV TRACKS! 🙄

[@derekspringer6448]

​@@T8ersaladBecause IV tracks need pen markings to be visible, and thus noticed by others. Totally. Those dingleberries... Its like, what are you even doing with your life if you aren't applying best practices to your daily intravenous drug use... Poking holes up and down anything even *resembling* a vein, until it blows out and is gone forever, is one thing... I draw the line at mapping out my veins with a ballpoint pen. What do you take me for? Some kinda delinquent? Yeesh.

[@Ziptietechnician]

Vivid imagination.

[@bgubs07]

I was given the same reason. This video makes much more sense though I guess.

[@CrazySparkie63]

I've seen LED streetlights in London UK turning green or purple, some as little as 6 months old, but more so in the winter, possibly due to thermal expansion and contraction!

[@blackmoon9511]

I've been looking for this info and it just so happened to show up on my feed months after I stopped searching. You, Sir, earned yourself a sub

[@ForeverThen]

12:42 when you paint the exterior of the lens, the light that phosphorizes will be scattered and decoherent to the focused beam the lens produces. Better to paint the inside lens surface, that way the scattered posphor light has a chance to collimate into a beam with the rest of the blue light

[@ericnewton5720]

My goodness that’s even more infuriating how they’ve known what is a good design and what’s bad, and they forced all these state and local governments into buying absolute garbage for 10x what it would’ve cost just replacing the sodium lamps with new sodium lamps.

[@fcbrants]

Thank you!! I've been completely baffled why they were installing purple LED's.

[@sivalley]

I remember when Phillips introduced some of the first high output "white" LED lamps with a remote phosphor. They had the packaging marked up to let consumers know the output light is white because the remote phosphor was such an intense yellow commonly associated with bug lights. Honestly, street lights and other heavily thermally cycled lights like these should have been designed with remote phosphor inserts that can be replaced easily and/or more easily color temperature binned. Edit: Wow, I need to watch the whole video before commenting, you did prove my thought process. 😅

[@Gripen047]

Those Philips L-prize bulbs were such a cool (but odd-looking) product when it came to market, but was way too expensive at first. My brother still has two of them for his garage and they still work, 13 years or so later.

[@nickwilliams2745]

From my understanding (engineer working with LEDs) is that the conformal coating that’s supposed to be protecting the phosphorus is what’s degrading too fast and causing the fail, but I don’t work specifically with street lamps so don’t quote me The specific phosphorus they’re getting from their supplier is widely used in industry so that specifically doesn’t see to be the problem but who’s to say Good video

[@jpdemer5]

"These are blue LEDs with a yellow phosphor on them." Well, there's the answer, @0:58.

[@JamesPotts]

Around here, the manufacturer is replacing them. The state DOT got hit with a tremendous number. The manufacturer claimed it was a flaw in the formulation.

[@100pyatt]

@@JamesPotts yes and potentially an eye damaging risk to the public as well

[@Sadler2010]

Exactly what I heard around the time these started showing up... And not too outlandish as the phosphor layer is falling of the chips.

[@jeffschroeder4805]

Wow! The color rendition difference was incredible...... and it did appear brighter though the camera may be compensating. Very interesting

[@MrTsolar]

What about the ones that are purple from day 1? Design choice or really cheap lights? Honestly, the biggest problem I have with high output LED lights like street lamps and parking lot lights is strobing. I can’t believe the number of strobing lamps that are out there. Makes me miss the orange sodium lamps that became prevalent in the late 80’s and 90’s. They are probably better for our circadian rhythm anyway, and I’ve heard the power consumption isn’t much more than current LED lamps.

[@VEC7ORlt]

Difference in power consumption is about twice due to scotopic/photopic difference LED lamps can benefit from.

[@IntegerOfDoom]

Night isn't night anymore. Everything is too bright.

[@poiiihy]

they must have came defective from the factory...

[@ethernet01]

HPS and flourescent are over 100 years old yet still impressively efficient and long life and they dont attack photosensitive people

[@VEC7ORlt]

@@ethernet01 define 'impressively efficient'

[@BillWalkerWarren]

Ok Phoenix resident here. This explains a lot . I have to say that the lights in my neighborhood went bad fast . It was under 2 years. One thing I did notice was the bad ( blue ) lamps did work better during a dust storm. Not sure why. Thanks for the video.

[@keithgraver5482]

I live in Connecticut and new lights with complete posts and power were installed in a long I84. The blue color started as soon as they were installed. I drive 84 everyday and never saw the white light. So that would mean they came broken?......

[@OrionsArm]

I mean the bluish ultraviolet color light looks way nicer than the harsh white light. Why not skip the phosphor lamination or maybe use red LEDs to preserve better night vision and prevent disruption to wildlife.

[@Arcella1981]

for painting the "lens" of the lamps, I think if I were to do this fix my self i probably would have painted the inside of the lens instead of the outside, this would do a couple things, would make it less likely to come off over time, because it would be more protected from the elements and also it would be closer to the LED and would most likely convert more light into the white usable light, because when you painted it, it is better but you can still see from your wall and the Samsung box, there is still some blue light getting out, I suspect that is from the light getting diffused through the acrylic lens from the other side of the paint. Now this is just speculation on my part, and you probably have done multiple tests on how to do this and is just showing us the best experiment, also I JUST now got to the end of the video and I now think this solution was best because you don't need to take the light apart to do this fix, basically just my 2 cents

[@harrysmbdgs]

I agree 100% the phosphor should be painted on the inside of the lens. Painting the inside would also mean the lens itself would still work, because the phosphor would be at the exact point from which the lens gathers light!

[@Torbjorn.Lindgren]

OTOH, painting on the outside can be done without dissasembling the light. Yes, he did that here to show what was going on but ideally you really don't want to have to spend that much time on it. With a good epoxy it's likely far cheaper to just reapply the paint it if necessary X years down the line. And I suspect that with some experimentation it should be possible to find an epoxy which will last longer than the expected remaining lifetime. Also, putting it on the outside of the lens likely means it's a big colder than if it's stuck directly to the LED module - and heat can break down some phosphors. So painting on the outside may mean you can use cheaper phosphors, not sure how resistant the cheap YAG phosphor is (it may be a non-issue).

[@tonywoodford9164]

Easy solution. stick some clear film over the top or stick clear film impregnated with correct stuff and dust stick this label on each lamp

[@HenryLoenwind]

@@harrysmbdgs For the ens to work as designed, it does not matter if the paint is on the inside or outside. The lens is designed to bend light coming from a fixed point at a certain distance, i.e. light that has a certain directionality. Light emitted from the paint that's touching the lens is emitted in all directions; only a tiny amount of it is in the right direction.

[@harrysmbdgs]

@@HenryLoenwind Of course, I had forgotten that the direction of light entering the lens also matters! I do think it would still work a bit better on the inside, but yes you’re absolutely right that the lens still wouldn’t be working as designed.

[@jackielinde7568]

0:10 - HEY! I know where the shot on the left was taken. It's off 7th street north of downtown. Driven by it MANY times. Couldn't say where the other two shots are.

[@tricki8352]

Was there a point in the video that he fully broke down the frame as well? I’d like to see if either of these are 5G lights.

[@kurifodomokuzai6667]

I'm a truck driver and most of all these blue lights I've seen are in Lincoln, Nebraska but are becoming common in other cities as well.

[@scottouimet2865]

We have a bunch turning this color here in albuquerque. It actually super nice to walk under them at night

[@JTA1961]

Well said...Roswell also agrees 👽

[@100pyatt]

Watch for eye damage anything under 450nm is dangerous

[@Skinflaps_Meatslapper]

@@JTA1961 You guys okay up there? I heard there was a lot of flooding not too long ago.

[@horseathalt7308]

@@100pyatt Bingo that ultraviolet light will blind you! Few people know this.

[@ReNiCGaming]

Thank you! I was very curious on why I was seeing purple everywhere.

[@Daniel-vh9lg]

Number one problem, HEAT! These LED's run HOT!! making the phosphor resin binder very brittle and crumbly. I see this happening more around train tracks and bridges due to vibrations. Sure wish I could buy up the ones that turned violet/blue.

[@psirvent8]

So basically heat brittles the phosphor and vibrations remove it ?

[@Daniel-vh9lg]

@@psirvent8 Exactly! The silicon capped ones are a lot better for commercial use.

[@GOPRepubliklan]

Great product for Phoenix then!

[@100pyatt]

@@GOPRepubliklan perfect for such an Arctic climate yep 🤣

[@jimleaveck1986]

Now listen up steetlite people. Here's a market 4 ur dysfuncional equipment

[@jessebob325]

I saw my first streetlight turned blue here in the UK. And I remembered your video. 👍🏻🍻

[@reedr1659]

I saw this phenomenon down in Phoenix, AZ and figured it was intentional for decorative purposes. Thanks for making the video.

[@SpaceDad42]

It was intentional, for other reasons.

[@Blubb5000]

I have seen many blue street lights from air planes. I was always wondering what that is about. Now I know. Thanks!

[@oahts5906]

Unfortunately he’s wrong about it. They are here intentionally

[@bimmons9975]

@@oahts5906that’s what I thought, like how did people keep ordering the same light with enough time to realize they’re broken. I assumed it would be part of some kind of tracking/ camera system or something

[@deniselee1900]

I suspect such a fix wouldn't pass muster, the lenses no longer beam, expecting a typ lambertian (but acts like diffuser as in COB LED), street lighting very likely have ordinance stating field and brightness... But such is an epic failure from the manufactuer

[@NanoPalomaki]

Definitely the light distribution would be impacted, but I still think it would be better than what’s out there now.

[@kcgunesq]

Its almost like some of us that knew that LED streetlights were a bad idea were on to something.

[@MrOiram46]

They’re setting up for a dystopia with that Terminator 2 blue-ish lighting 😂

[@Muzzleblast-1911]

I've seen them put these new lights up and they were never white. Always or already purple as soon as they fire them up.

[@mjmeans7983]

The ultimate cause seems to be the use of a product not suited for the specific environment in Pheonix precipitated by a combination of factors around the lowest-bidder government procurement process, such as lax specifications in the tender, lower quality product selection by the vendor, and/or government inspection that failed to adequately do their job.

[@JTA1961]

Last sentence... 8 words... how nice to be...them.

[@Sadler2010]

Failing everywhere, seeing them around the larger metro areas near Milwaukee, WI but not so much here in little old Racine. First noticed nearly 2 years ago around Franklin, Oak Creek, and Hales Corners. These are "bedroom communities" so they have good tax revenues there, to buy fancy new lights that fail..

[@markanderson3707]

Initially, when I started this video I was relatively sure it would be about as interesting as watching paint dry. And while parts of the video approach the thrill of drying paint, it really never gets there, and is surprisingly interesting and informative. But then I’m an artist, so CRI and color temperature are terms I know, and look for, when purchasing lamps or fixtures for the studio and my home. Also, I like watching paint dry.

[@AdricM]

where did you get your Yag Phosphor? ive managed to scavvenge a teeny bit from dead led lightbulbs using a tolulene bath.. but ive never found a supplier of the phosphors.. been thinking of trying to recover the phosphors from some florescent bulbs too.

[@gregorymalchuk272]

Fluorescent tubes use totally different phosphors.

[@AdricM]

@@gregorymalchuk272 indeed, although finding info on them is really tough..

[@seldoon_nemar]

This explains so much. there's a section of highway i go though occasionally where the lights have done this, but it's only one section... It's because that particular streach had an improvement/upgrade at a different time than the rest of the system

[@c.b.kansan1700]

I've noticed this around my neck-o-the-woods too. Quite impressive with a good layer of snow on the ground. Almost blinding.

[@thom1218]

Remember when street lights had nice glass globes with soft warm HPS bulbs in them, especially in older residential neighborhoods? They had to rip all those out to fit eye gouging awful LEDs that couldn't accommodate a shroud of glass. Now they all look like harsh stockyard lights, with horribly bodged retrofit jobs fit for a prison encampment or some other dystopian nightmare - but at least they have good color rendering indices, right?!

[@W8iHav2P]

Those old light sucked, barely allowed you to see anything. Get over it 😂

[@tripleaffirmative5p]

HPS was bright enough, you have headlights, flashlights are cheap enough, and they were for more for visibility without disrupting night vision not being able to see every little detail

[@ethernet01]

LEDs dont belong on residential streets let one sleep again great at their job on highways for 3-6 years before they become a killer of epileptic people or a grow light

[@VEC7ORlt]

@@ethernet01 stop talking nonsense about things you know nothing about, also epileptics aren't allowed to drive.

[@lampmunchertv3861]

@kennethney4260 ur just blind.

[@Cammi_Rosalie]

LED manufacturers need to focus more on a warmer, 3000 to 3500 K light. This cold blue/gray light is irritating. Especially in car headlights. I have LED bulbs in all of my fixtures at home. All of them warm white light. The phosphor coating is more orange then the cold-white lights. so why do they not use the warmer phosphor coating on street lights and headlights? Warmer light is is far less harsh, easier to recover from the glare when going from illuminated areas to dark areas. And would be far better in car headlights than the current (And infuriatingly squint inducing) harsh blue/gray light. I also never see any "white" light from any of these. To me it looks like a sickly blue-gray color, similar to the fluorescent lighting that gave me headaches and stinging eyes for 13 years in school. I hate it.

[@jimmer411]

I'm in the opposite side of the spectrum, I absolutely hate warm light. The yellow/orange tint makes everything look unnatural to me

[@VEC7ORlt]

@@Cammi_Rosalie they don't use warm white in headlights and streetlights because of the photopic/scotopic ratio - you see better and further under colder spectrum. Also lights do not make your eyes sting, its literally the anything else but the spectrum.

[@100pyatt]

The white light achieves higher visibility with less energy that's why. The soft white is not as efficient due to spectrum

[@jeffkardosjr.3825]

​@@VEC7ORltThat's nonsense.

[@VEC7ORlt]

@@jeffkardosjr.3825 oh rly?

[@bigjd2k]

LED streetlights are a crap idea - they only light up the ground underneath (no spread), they’re glary but also older ones are very dingy, they can’t be repaired like the old units (the whole fitting gets swapped), and they’re made abroad. Total disaster for a slight increase in efficiency. Should never have been allowed. They’re heavy too and tend to work loose in high winds. And they don’t actually last that long anyway. Bring back high-pressure sodium - lamps were doing 80,000 hours plus before they were phased out - way longer than any LED fitting will last.

[@JTA1961]

Get that "orange" man back "in" & make that request again...😊

[@100pyatt]

That's just simply false and based on total ignorance And nobody is going to remove fuel injection from their car either to install carburetors.

[@gregorymalchuk272]

​@@100pyatt The cold starting alone makes fuel injection worth it.

[@jimmay8627]

Street lights here in Vancouver BC were already doing this when I moved here in 2021. I knew it was the phosphor coming off. What I didn't know was that the reason why it was coming off was that there was nothing there to retain it - no silicone domes (as you see on the new units). Silicone domes serve to increase efficiency by reducing the amount of total internal reflection due to the IOR difference at the surface of emission. They also happen to double as a holder for the phosphor for direct-on-die emitters. Dedomes emitters sacrifice some efficiency/total output in favor of a smaller/more intense emitter surface - useful for lights with narrow emission uses, spotlights, flashlights etc. Back in the day, flashlight nerds would intentionally dedome emitters to get that extra throw (it took some skill to do it without ripping off the phosphor and ending up with a blue emitter). Domed emitters were the choice for max lumens per watt, floodlight type applications. Like streetlights. If they'd stuck with domed emitters like you should see in applications like this, we'd likely not have noticed anything for a few years more.

[@DELAWAREBOWHUNTER]

Jesus Christ! I thought my eyes were going bad, and I was developing cataracts! Here all along. It was just the fucking street lights! I need a beer

[@buckykattnj]

I imagine it would be a tough sell to get maintenance people to start painting the LED lenses... and much easier to make a thin steel plate with a window that would have a sheet of phosphor tinted plastic... then maintenance people could attach them by using the four screws already on the lamps.

[@lwilton]

Maint people aren't going to do this, period. Three reasons: 1) it would take longer than replacing the streetlight, 2) it would void the manufacturer's warranty, and 3) if someone had an accident under or near a repaired light, they could sue the city for billions, claiming the repair caused them to run drunkenly into a school bus full of children during the day. (And they would win. That's how the court system works.) It's the same reason that if a piece of city-owned playground equipment needs a minor repair part that you can get from Home Depot for a dollar, the entire piece of equipment will be scrapped if the part can't be sourced from the equipment manufacturer. Replacing the part with an identical one of their own opens them to liability when someone misuses the equipment and injures themselves or someone else.

[@travismiller5548]

​@lwilton it was a good idea; you're wrong. i've installed new and serviced existing streetlights. 1)there's room for some .030, even .063 or thicker material. the screws too would accomodate this, as evidenced by the streetlight i have on my workbench RIGHT NOW. (i checked.) 2) we've been discussing work that is outside of any warranty, try to pay attention. 3) billions? seriously, you're being overly dramatic.

[@travismiller5548]

it's an excellent idea. one can get lazer cut, thin stainless sheet quite cheaply and quickly from companies like JLCPCB, for applying solder paste. i'm totally doing this. we're going to laugh at this naysayer all the way to the bank in Des Moines, Iowa.

[@williamroark4760]

You initially described the issue as a "failing" street lamp. In south central KY, the purple color came from brand new LED street lamps. They blamed it on an incorrect order/manufacturer defect.

[@elektro3000]

I've seen these both in Phoenix, AZ and in Ann Arbor, MI at the University of Michigan North (Engineering) Campus. I always thought they were designed to be purplish blue, never knew it was a failure. Great explanation and prototype fix, thanks!

[@robot_madness3164]

There are actually fixtures designed to do both for architectural lighting (with a data control system for automation). There may be a chance they are this type if they are lights on campus or parking lots, ofc even more unlikely outside of that.

[@RHEC1776]

They aren't failing. They help you see better

[@elektro3000]

@robot_madness3164 The ones at U of M are on a street alongside the Ford Robotics Building, across from a parking lot. Not sure if they might be for some aesthetic purpose, but it seems odd to have less-effective lighting shining directly down on a road.

[@elektro3000]

@RHEC1776 I mean yes, they still shine light, but as this video demonstrates, they only help about one quarter as much as before the phosphor breaks off.

[@Sadler2010]

I forget how/where, but not too long after I started seeing these around I did hear it explained as a defect in chemistry, which tracks as the Phosphor layer is delaminating in the failed lights.

[@leewm.gaudry3770]

Question one not including labour, what would the materials cost for each light? Seems to me this could work as a cottage industry. Q2: have there been accidents caused by weird lighting in the areas where this is common? Q3: what seems to be the cause of the delaminating a.temperature variations b.vibration from wind, traffic. C.variations in humidity.

[@cts3696]

I was driving on I-84 near Scranton once and saw blue lights and was very confused, nice to see why they’re there

[@CryptoTonight9393]

Damn i was hoping it was a new kind of light, i love the colour purple and thought they looked awesome.

[@derekspringer6448]

I thought I was alone in this

[@BassMaann]

I’m with ya, there’s a whole highway exit in my city that has all the lights purple, so cool at night

[@amyb7823]

Meee too! 😂

[@BobsTank]

I had this happen to an indoor LED bulb a few years back. I took it apart to see why it was emitting patches of 'purple' light. I pretty much knew what you were going to find when I began watching this video.

[@tobiaslollesgaard7389]

But why did it happen are they just overly cheap lamps?

[@shockfactorobi]

The biggest theory is that testing was not done outdoors with the actual sun beating down and heating the lamp heads. So originally they were only placing a small amount phosphur without the added thermal silicone protection, as seen in the newer, replacement board. The sun causes more heat and expansion than the LEDs themselves for what the design was rated for.

[@LawrenceGerske-nb2eo]

When Phoenix first started replacing the HPS (High Pressure Sodium) lights with LED, the city specified a 27K (kelvin color temperature) to keep the orange lighting affect instead of producing a white light. As you reported the older fixtures did start producing a purple light. I can't confirm what the city is now replacing the failed fixtures with, but to emphasize the original intent was to have a light output that was similar to the HPS fixtures not a white light output.

[@dawlben2247]

Why did they not go for a yellowish hue?

[@qx4n9e1xp]

I LOVE seeing that occasional blue light.. They're a vibe!

[@amyb7823]

Hell yeah! 😂

[@riflebear1711]

Ugliest fake blue light ive ever seen. Somethings wrong with you

[@MikeHarris1984]

I've been wondering this for so long! About 6 years ago, the city of Phoenix went through and replaced every single street light in the entire city on major in neighborhood roads everywhere with LED. And over the past two years or so I've noticed in sections entire streets will suddenly glow purple one night and then they'll be like that for a few weeks and then I guess the city comes by and replaces them. I've reached out to ADOT, City of Phoenix, City of Glendale, City of Peoria, and well all the cities and they always answer any other questions I post on Twitter to them or even opening up tickets with their infrastructure system to report issues and nobody ever responds with what's going on with the traffic lights turning purple all of a sudden. And my main issue is, if my tax dollars are having to be spent to replace the traffic lights multiple times every single traffic light in the city and the cost associated with that with Cruz going out finding the issues replacing them fixing them after they had already spent the hundreds of millions of dollars to replace every street light in the city to begin with few years prior. So it's frustrating whenever the city or nobody will reply back to say what the hell is going on

[@JTA1961]

Whataya gonna do...? Call the popo...? They're all held unaCOUNTable

[@tobiaslollesgaard7389]

In europe we have had led streetlamps for years and i have never seen this.

[@mlies37]

I’m in Europe too and it’s happening all over town with streetlights

[@SIBUK]

I'm in the UK and have never seen it either. I hope it starts happening though! Can't stand these LED lights.

[@100pyatt]

Chinese LEDs ✅

[@Sadler2010]

It is just one manufacturer that has this issue...

[@GonzalezSix67]

The bright white annoys me. Way too bright at times. During hard rain, hard to see the white stripe lines on the road, with the bright white LED lights. Same with snowy conditions

[@KevinT3141]

I had a bunch of those Philips bug-eye bulbs in my condo 15+ years ago, despite the expense they were worth it to not heat the place up so much in summer. The bathroom and dining room (well beyond the range of the window mounted air conditioner) stayed noticeably cooler. They're still going today in our home's garage door opener.

[@ericnewton5720]

Nobody is used to this garbage white light. It’s always been orange sodium lamps that were extremely efficient when they were running. And they weren’t so stark that you get halos in your eyes and when transitioning from lit area to unlit area it wasn’t so stark. These bright white daylight color temperature LED street lamps are fucking terrible. I have one that shines directly into my windows at night, and they are the definition of hell spawn.

[@100pyatt]

HPS uses 100x more power it's not efficient whatsoever

[@mikafoxx2717]

​@@100pyatt100x is a pretty crazy exaggeration. Maybe like 30%. HPS is 100-150 lumens a watt, wheras a household LED might be 13 watts for a 1600 lumen bulb.. 123 lumens a watt, though for a much much higher CRI. Cool white and low CRI is also more efficient.

[@FATMAN_tactical]

would recommend doing you best to block that street light, the blue wave lengths of light can affect your sleep

[@100pyatt]

@@mikafoxx2717 yes 100x is an exaggeration. Realistically it's about 600-1,000% more power needed on most HPS lights VS LEDs that's are properly under driven for efficiency and lifespan, that's why the HPS lights needed to be gone. It's a dramatic reduction in power consumption with the LEDs

[@mikafoxx2717]

@@100pyatt Properly driven for longevity and lifespan.. so NOT the ones they're using now and probably never will use. Also consider the cost of replacing all the bad led street lamps that turned blue because the phosphors fell off. I read a paper on some calculations and they estimated only 36% money saved, not even accounting for that faulty led issue.

[@ukar69]

In reality, nobody is going to fix them, they'll just be replaced, in many cases with the same model. No incentive to save money when that money is coming from the public.

[@TheCatherineCC]

In many cities they're being replaced under warranty. Sodium was so expensive for cities with labor on bulb replacement and power, led companies could undercut them and have enough profit to do these massive recalls.

[@pfoxhound]

Because of corruption. Your city approves cheap projectors, sold with high price. Corruption. No responsibility.

[@jimmay8627]

Lighting nerd nitpick: 11:10 That's not the L Prize winner, but its predecessor. I have examples of both. The L Prize bulb had the same structure, but with a white body without fluting instead of the silver, and the remote phosphors had a lemon yellow appearance instead of the egg yolk color. It also had other emitters in addition to blue ones - IIRC they were orange, to pull the color temp to 2700K instead of the 5000K it would otherwise be.

[@Josh-wu7kz]

We have these purple street lights in the town centre of Stockport in the UK.

[@Hide.the.Salami]

Good to know for sure those ones are broken and why! Thank you!

[@TomMinnick]

Could they add phosphour into the acrylic when they cast the lenses? This would embed the acrylic into the material. There would be no way for it to separate then?

[@joshuap8224]

This was an issue before this video publish date first indication on the Middle East coast was 2019-2020

[@edwardgiovannelli5191]

So did you compare the useful light output of the 'repaired' lamp versus the new lamp? That's the real test to see if the fix is really good or not

[@alanreece9829]

I have known that the blue lights are technically bad but I much prefer them to the bright white at night as the blue is easier on my eyes at night