Nichia Develops 60 Lumen Per Watt White LED

[jtr1962]

It's not just the cost of CF bulbs that turns people off. It's also the fact that they don't last as long as claimed when turned on and off frequently. People just don't get it that you can't turn a fluorescent on and off constantly. LEDs don't suffer from this problem. I also wouldn't be surprised if the yellowish color of most easily available CF bulbs is also another turn off. The light manufacturers assume that a person replacing an incandescent with a CFL wants the same type of yellowish light while that might not necessarily be true. While you can get CFLs in other color temps, they are not that easy to find except via mail order.

Regarding the ornamental lights you mentioned, I'll guess that those will be one of the first things for which LED replacements are made since they are among the least efficient types of incandescent made (8 to 10 lm/W ). While they do have CF replacements for those now, they aren't a point source like an incandescent so they don't have the same sparkle. LEDs are close to a point source so they will be a suitable replacement. Also, some LEDs under development will eventually mimic sunlight extremely closely (~5500K CCT), and will provide a much superior light quality compared to the very yellowish light coming from typical ornamental bulbs(~2400K). Fixtures with glass crystals, for example, will look much better with the truer, whiter light as the entire spectrum will be represented (incandescents are relatively deficient in shorter wavelengths such as violets, blues, and greens).

 

[sechs]

I always work on the presumption that about half of the life of a CF is lost in the way that I use the bulb. The reason that I use them, however, is the efficiency, not the longer life.

As one who lives in an appartment which lacks a proper number of ceiling fixtures, most of my rooms have a lamp. It's much easier to light a room with a single 45watt compact fluorescent than multiple 60watt incondescents.

 

[ddrueding]

I use CFLs becuase of the color temp. I don't care if they're half as efficient with half the lifespan of an incandecent. I figure that with my usage pattern, it should average about the same lifespan as a standard bulb. :shrug:

 

[e_dawg]

I still don't like CFL's because of their colour temp and rendition. It's either yellowish 2700 K or bluish 6500 K with a CRI in the low 80's. My definition of white light is around 4000 K and a CRI approaching 100. So far, the only light source that truly satisfies me is those neodymium coated incandescents: GE Reveal and Sylvania Daylight. (I can't find a Philips equivalent; too bad, because my Home Depot only carries Philips)

The PAR20/30 halogen reflector floods are my other choice for ceiling fixtures where the light requirement is higher. Not as white as the neodymium incandescents, but they are more 50-70% more efficient (halogen makes them 30-40% more efficient, and the reflector configuration makes them 40-50% more efficient than a non-reflector bulb, where half the light gets trapped in the fixture) and are whiter than normal incandescents (3000 K vs 2700 K).

 

[e_dawg]

As one who lives in an appartment which lacks a proper number of ceiling fixtures, most of my rooms have a lamp. It's much easier to light a room with a single 45watt compact fluorescent than multiple 60watt incondescents.

Have you tried PAR20/30 halogen (or even R20/30) Reflector floods? I needed maximum light output from a limited amount of fixtures. Most of these fixtures are recessed into the ceiling, so a typical incandescent loses half of its light output inside the fixture. Switching to halogen reflector type bulbs made a huge difference for me. For example, the 75 W PAR30L halogen reflector floods I use put out as much light as regular 150 W incandescents. I use two of them in one room, and it's actually pretty bright in there. If you look at them, it's like staring into the sun.

 

[e_dawg]

And just in case you were wondering whether these PAR20/30 and R20/30 bulbs were compatible with your existing fixtures/sockets, yes they are. (I wasn't sure if they would fit the sockets or the fixtures properly at first, but they are a direct drop in... PAR38 might be too big for most fixtures, though)

 

[jtr1962]

I still don't like CFL's because of their colour temp and rendition. It's either yellowish 2700 K or bluish 6500 K with a CRI in the low 80's. My definition of white light is around 4000 K and a CRI approaching 100. So far, the only light source that truly satisfies me is those neodymium coated incandescents: GE Reveal and Sylvania Daylight. (I can't find a Philips equivalent; too bad, because my Home Depot only carries Philips)

This place has CFLs with a 5500K color temp and a CRI of 91. They are a bit pricey, but if you buy 12 or more you get free shipping. Subjectively, 5000K to 5500K is about as white as it gets. If the color temp is higher, the light does look noticeably bluish. Any lower and it looks yellowish. This isn't 100% true as your eye has an auto-white balance of sorts but when I've put an apparently white 4100K tube next to a 5000K tube it does look noticeably yellowish. To get an idea of the type of light these CFLs put out, you might want to try those GE Sunshine tubes you mentioned in ddrueding's thread on 6500K CFLs. Not bluish at all but as white as white gets.

BTW, there are LEDs under development that you'll probably like. These use UV and a RGB phosphor to get a CRI close to 100. Besides efficiency, there are still some issues before they go into production. For example, UV LEDs don't last long because the UV destroys the semiconductor. Eventually, this will be fixed but it will be a while.

I heard the halogen reflector floods put out a relatively large amount of light for their size, although the light is still too yellowish for my tastes, and the efficiency doesn't come anywhere near a state of the art fluorescent light. My bedroom fixture uses 102 watts and the room is very bright. I have 210 watts (according to the ballast specs) of fluorescent lighting in my 77 ft² workroom (4 40W T-12 tubes and 2 32W T-8 tubes), and it looks almost like daylight in there. When my GE Sunshine tubes go and I replace them with the 3600 lumen ones I mentioned in the other thread the room will be brighter yet (~19000 lumens total). BTW, I need these lighting levels for the close work I do, and I find task lighting annoying (too shadowy) so I need to light up the whole room like a ballpark.

 

[sechs]

Have you tried PAR20/30 halogen (or even R20/30) Reflector floods? I needed maximum light output from a limited amount of fixtures. Most of these fixtures are recessed into the ceiling, so a typical incandescent loses half of its light output inside the fixture. Switching to halogen reflector type bulbs made a huge difference for me. For example, the 75 W PAR30L halogen reflector floods I use put out as much light as regular 150 W incandescents. I use two of them in one room, and it's actually pretty bright in there. If you look at them, it's like staring into the sun.

The 45W CFLs put out about as much light as a 180W incandescent. So, for less wattage, I get more light than the halogen; and I stay under the 60W limit of most of the lamps.

 

[e_dawg]

They are a bit pricey, but if you buy 12 or more you get free shipping.

alas, but not to Canada...

Subjectively, 5000K to 5500K is about as white as it gets. If the color temp is higher, the light does look noticeably bluish. Any lower and it looks yellowish. [...] To get an idea of the type of light these CFLs put out, you might want to try those GE Sunshine tubes you mentioned in ddrueding's thread on 6500K CFLs. Not bluish at all but as white as white gets.

To me, 4500-5000 K is about pure white, and 4000-4500 K looks like todays' sunlight (granted, it is winter)... but I prefer 3500-4000 K in the bed/bath/living room for aesthetic reasons (those 3700 K/91 CRI GE/Philips "natural" tubes would be perfect). I could go with anything up to 5500 K in working areas, I guess, but in general, anything over 5000 K I would consider bluish.

I have looked at those GE Sunshine tubes quite a bit over the last few months, and they still look a little bluish to me. Not very blue like those 6500 K "daylight" tubes, but still on the blue side for me. 4100 K cool white is actually my favourite all-purpose flourescent colour temp. If they made one with a CRI in the high 90's, I would drive down to the US myself and pick them up.

BTW, there are LEDs under development that you'll probably like. [...] there are still some issues before they go into production. [...] Eventually, this will be fixed but it will be a while.

Yep. Yet another thing to add that to the list of things I will have to wait a decade for...

I heard the halogen reflector floods put out a relatively large amount of light for their size, although the light is still too yellowish for my tastes

Yes, I also think they are a little too yellowish to be ideal, but at the end of the day, I still prefer their 3000 K CCT / 100 CRI to other alternatives.

My bedroom fixture uses 102 watts and the room is very bright. I have 210 watts (according to the ballast specs) of fluorescent lighting in my 77 ft² workroom (4 40W T-12 tubes and 2 32W T-8 tubes), and it looks almost like daylight in there. When my GE Sunshine tubes go and I replace them with the 3600 lumen ones I mentioned in the other thread the room will be brighter yet (~19000 lumens total). [...] like a ballpark

I can already picture the retina searing brightness

I think you should convert your home into a Seasonal Affective Disorder treatment center. I can see the advertising flyers now: "Spend a hour a couple times a week in jtr's work room and burn away those winter blues!"

 

[jtr1962]

4100 K cool white is actually my favourite all-purpose flourescent colour temp. If they made one with a CRI in the high 90's, I would drive down to the US myself and pick them up.

You might be interested in Sylvania's cool white deluxe tubes then. We bought 3 ten-packs a while ago, and I noticed the better color immediately, especially the reds. After I got interested in light, I checked for the specs online. The color temp is 4100K, like all cool whites, and the CRI is 89. I just haven't seen anything better with a 4100K color temp. There are T-8 tubes made by all three major manufacturers (GE, Philips, Sylvania) which have a CRI of 86 and a color temp of 4100K, but of course you need a fixture that accepts them. The Sylvanias I mentioned are T-12. Like all high CRI tubes, efficiency is somewhat less (output is 2200 lumens) but that's the tradeoff. The GE/Philips natural tubes you mentioned also have low efficiency. When LED lighting is the norm, high efficiency and CRI will be possible because of the very small amount of phosphor needed, meaning you can use more expensive phosphors.

I'll admit somewhat that 5000K and up might take some getting used to, especially when you've only had incandescents and cool-white fluorescents before that. There might be a touch of blue there, but in isolation it looks white (so does anything from about 3500K up to around 6000K thanks to the eye's auto-white balance that I mentioned).

I can already picture the retina searing brightness

I think you should convert your home into a Seasonal Affective Disorder treatment center. I can see the advertising flyers now: "Spend a hour a couple times a week in jtr's work room and burn away those winter blues!"

8) Believe it or not, the bright light combined with the flicker free electronic ballasts has made me feel noticeably better when I need to work long hours. A few weeks ago I worked for 50 hours straight and didn't have the usual headaches. Last time I did that a few years ago my head hurt terribly, but that was before I changed out the ballasts in my shoplights for electronic ones. The simple fact is that typical lighting levels, especially in most people's homes, are far too low. Granted, some of this has to do with practicality as bright lighting with incandescents requires a ridiculous amount of power, and not everyone likes fluorescent lighting. Still, I would like to see more homes, especially areas like kitchens, workrooms, and baths, brightly lit.

It is only now that we're discovering how important light really is, and I'm thinking that the typical low color temp lighting frequently chosen for homes by lighting designers for alleged aesthetic reasons (even though I think it looks horrible) is a very poor choice both for health and actually doing any tasks. It also makes chosing color schemes a nightmare as things look radically different at night under artificial lighting. This is quite unlike my bedroom which looks virtually the same day or night. I'm quite sure a lighting designer would cringe at my lighting preference, at least until I explained my reasons.

 

[ddrueding]

8) Believe it or not, the bright light combined with the flicker free electronic ballasts has made me feel noticeably better when I need to work long hours. A few weeks ago I worked for 50 hours straight and didn't have the usual headaches. Last time I did that a few years ago my head hurt terribly, but that was before I changed out the ballasts in my shoplights for electronic ones.

I'm considering making a light bazooka over my workbench for this reason. I was looking at the other thread and it's discussion of over-driving bulbs and some of the larger 4-bulb fixtures. My workbench is 3 feet deep and about 8 feet long. It would be an interesting experiment to see how much light I could stick over it

 

[e_dawg]

You might be interested in Sylvania's cool white deluxe tubes then. [...] The color temp is 4100K, like all cool whites, and the CRI is 89. I just haven't seen anything better with a 4100K color temp.

Indeed. That seems to be the best you can get these days. I know Philips produces T-12's with the same specs: Daylight Deluxe, 4200 K, 89 CRI, 2200 lumens. I am trying to find a Home Depot that carries them. I might try asking them to special order them for me, although I won't be needing them just yet as my kitchen tubes still have at least a year's worth of life left in them. I am tempted, however, to replace them earlier just to get the better light quality, as good quality lighting just makes everything better. I know you obviously feel the same way.

 

[e_dawg]

Daylight Deluxe, 4200 K, 89 CRI, 2200 lumens

I meant Deluxe Cool White, of course...

 

[e_dawg]

I forgot to mention that the reason it would have to be Philips is that I can't get Sylvania flourescents around here. The only Sylvania lighting products I can get locally are incandescents (and only from the local supermarket!). Home Depot carries selected Philips incandescents and flourescents. Canadian Tire carries selected GE incandescents and flourescents.

I would order more lighting products online, but the shipping & taxes to Canada make it prohibitive.

 

[jtr1962]

I'm considering making a light bazooka over my workbench for this reason. I was looking at the other thread and it's discussion of over-driving bulbs and some of the larger 4-bulb fixtures. My workbench is 3 feet deep and about 8 feet long. It would be an interesting experiment to see how much light I could stick over it

Thinking about this a bit, you could get the shoplights two across and four deep, which means you could have 8 shoplights above your workbench. When overdriven as per that article, you get about 10,000 lumens each. That's 80,000 lumens over 24 ft², or 3333 lm/ft², which is very intense. Full sunlight at the equator is around 9000 lm/ft². If you do this, your setup should be able to double as a plant-growing area when not in use. :wink:

BTW, I opened up one of those ballasts both to have a look inside and to see if I could quiet it down. While some of those Home Depot shoplights are quiet, some also have a somewhat audible buzz. By replacing the plastic insulator with cardboard, and attaching it with silicon to the metal ballast case I was able to quiet the buzzing. There might also be a way to overdrive it simply by changing a resistor rather than using one ballast per tube as in the article. This would save the bother of using two ballasts per overdriven shoplight. If I come up with anything I'll let you know.

 

[.Nut]

http://litepanels.com/main.html

Another long-needed implementation of LED lighting source that solves the decades-old problem of having to deal with hot halogen lights and power cords.

 

[ddrueding]

http://litepanels.com/main.html

Another long-needed implementation of LED lighting source that solves the decades-old problem of having to deal with hot halogen lights and power cords.

Wow, not cheap.

 

[Gilbo]

If you do this, your setup should be able to double as a plant-growing area when not in use.

Speaking of lighting for growing plants, does anyone have advice on what would be the most efficient type of lighting to use? I have a bunch of plants which could use a little boost, particularly in the dark Halifax winter, but have no experience with hydroponics. Considering how much some of you know about lighting, I figured you might be able to give me an educated opinion.

I read some time ago that NASA was looking into using LEDs to grow plants in space, where electricity is in short supply, because they are so efficient. I don't know if generally available LEDs produce light of the appropriate wavelengths. I believe I have read that red LEDs are the most efficient right? I have definitely heard that white LEDs can be less efficient than some other types of lights (flourescents I assume?). Lastly I know that flourescents don't output evenly across the visible spectrum. Can they be used for growing plants?

For maximal efficiency plants need to have two seperate pigments excited. Efficient photosynthesis can't be completed without wavelengths less than or equal to 680nm --not in higher plants anyway. Do red LED's put out light lower than this? These pigments also absorb light in the blue and violet areas of the spectrum, and I know there are also blue LEDs. Perhaps they would be a better choice? There is more energy available from a quanta of blue light than red.

According to the information that I've been exposed to in the past, one pigment is happiest with ~410-440nm or ~670-690nm light, the other with ~460-475nm or ~650-670nm. Getting it smack dab in the middle of either of those ranges would be especially good, and, as I mentioned, an equivalent amount of blue light is likely to be better than an equivalent amount of red, but this is an inference, and I haven't encountered direct evidence for this. (The math says that a mole of 650nm photons is worth 184kJ, while a mole of 420nm photons is worth 285kJ. Additionally, the pigments have greater absorbance in the blue regions than they do in the red. Combined, those facts make a good case for blue.)

Anyone grow plants indoors with artificial light? Opinions?

 

[jtr1962]

I did encounter some information about growing plants in the course of my research. Here is a page comparing the effectiveness of different types of fluorescent tubes for plant growing in gory detail. NASA's studies using red and blue LEDs to grow plants are another interesting read. Here's some in brief articles here and here. See below for a comparison of wheat grown under different types of light:

Since plants are usually green this means they use the red and blue portions of the spectrum and reflect back the green. Incidentally, you can get LEDs emitting in all the ranges you mentioned, although blue centered at 470 nm and red around 655 nm and 635 nm are what is most readily available. In fact, since LEDs are narrowband emitters with a typical bandwidth of 30 or so nm if you get an LED whose center frequency is in the center of the range of interest, nearly 100% of the light will be useful to the plant. Furthermore, blue and red LEDs now typically have efficiencies well in excess of 30%, which is on par with the best fluorescents. However, since all of their light is in the band of interest, they are more efficient for plant growth than fluorescent tubes (and of course more expensive unfortunately). Nevertheless, in situations where power is at a premium LEDs are being seriously looked at for plant growth, and of course as time goes by they will only get cheaper and more efficient.

 

[jtr1962]

Bumping this thread a few days ago turned out to be very serendipitous indeed. It looks like it's time for another update

Quite a number of highlights here. Cree has their XT-24 blue chip in production with the XT-27 available in sample quantities. The XT-24 outputs 24 mW and the XT-27 outputs 27 mW, both when driven at 20 mA. Both outputs are centered around 460 nm, which is ideal for making white LEDs. Given the typical forward voltage drop of 3.2V, their outputs equate to 37.5% and 42.2% efficiency, respectively.

White leds made with the XT-27 have outputs of 5.2 lumens at a CCT of 6000K and 5.8 lumens at a CCT of 4600K. The corresponding efficiencies are 82 and 92 lm/W, respectively. Both of these efficiencies are well into the realm of linear fluorescent tubes. Funny, it doesn't seem like all that long ago when I started this thread that we were at 60 lm/W.

Cree also has made high power LEDs with efficiencies of 57 lm/W when driven at 350 mA and 34 lm/W driven at 1.4A.

How long it will take these improvements to make it out of the lab is anyone's guess but by all appearances 2005 looks to be a banner year for LEDs. LEDs with efficiencies ranging from 40 to 60 lm/W will finally see production. And I wouldn't be at all surprised if white LEDs broke the 100lm/W mark before year's end.

Also of interest, Osram made a red (618 nm) LED with a record efficiency of 108 lm/W.

In developments here at home, I haven't been around much here because I'm working on an interesting project involving LEDs myself. Read all about it here.

 

[mubs]

jtr, re. the taxicab ad project, a thought - have you considered remote source lighting? Years ago I interviewed with Remote Source Lighting Int'l, but can't find them on the web; maybe they went belly-up. Try a Google search on remote source lighting - there are many other hits.

 

[jtr1962]

Was this the company you're referring to?

Fiber optics isn't really something that this project calls for since we have plenty of room to put the LEDs in the sign. I do wish I had some 80 or 90 lm/W LEDs though.

 

[GIANT]

Scrumptious lighting technology and products:

http://colorkinetics.com/technologies/chromacore/page1.htm

 

[jtr1962]

Looks like the 100 lumen per watt barrier for white LEDs has finally been broken! :cheers: Amazing! We went from 60 to 100 in less than two years. At this rate we may be at the 2012 goal of 150 lm/W far sooner than expected. The future certainly looks bright (pun intended).

 

[Computer Generated Baby]

A wack idea I had once -- and is probably in use somewhere -- is to have digital electronic billboards based on either LCD or LED picture elements, obviating the use of imagery on paper or plastic. To update the signage, one simply uploads a new digital image to the billboard over a network connection. (Then hackers break in and start playing around with the billboard -- that's another story.)

 

[ddrueding]

A wack idea I had once -- and is probably in use somewhere -- is to have digital electronic billboards based on either LCD or LED picture elements, obviating the use of imagery on paper or plastic. To update the signage, one simply uploads a new digital image to the billboard over a network connection. (Then hackers break in and start playing around with the billboard -- that's another story.)

There's been one of these on Hwy 101 between San Jose and San Francisco since at least 1999.

 

[Platform]

There's been one of these on Hwy 101 between San Jose and San Francisco since at least 1999.

Yes, I've been seeing "electronic" billboards around here for years, too, but I was speaking of one that actually had a network connection of some sort (wired, wireless) that would allow updates from a remote operator.

 

[Platform]

LED Evolution Could Replace Light Bulbs

http://apnews.myway.com//article/20050415/D89FRHL00.html

• [list:65495a5332] [list:65495a5332]
  

[/list:u:65495a5332] [/list:u:65495a5332]

 

[jtr1962]

Thought I'd bump this thread because I've been doing some output and efficiency tests on some white LEDs I've gotten from eBay. Here is the thread with my results at CandlePower forums. Two years and 2 months after starting this thread it seems even the cheap white LEDs available on eBay are doing 40 to over 60 lumens per watt. I even had 100 from one seller that exceeded 70 lm/W!

It was nice to talk about this development when it was just in a lab. It's even nicer now to have some actual widely available samples in my hands which are capable of fluorescent light efficiency.

 

[Buck]

Wow! Excellent work jtr.

 

[i]

I think it's safe to say that the people affected were not vampires:

18 Burned by Faulty Gym Lighting

I'll be avoiding metal halide lights even more now.

 

[timwhit]

Wow. I had no idea that a lightbulb could do that kind of damage from that kind of distance. Usually gym ceilings are pretty high.

 

[i]

They often use those kind of lights at the Home Depot, Lowes, and other "warehouse" type stores. I'm sure on some occasions I've been able to feel warmth from them, despite them being waaaaay overhead. I'll be more suspicious about them from now on.

 

[ddrueding]

Hoping JTR is still reading this thread, as I think he may be the only one able to answer this question. I'm looking at replacing a number of the bulbs in my house with 6500K bulbs. I've already replaced the ones that were available at home depot, but some of the form factors are specific (flood, vanity, etc) and I have not been able to locate them locally. What would be the challenges in wiring an LED based solution to be driven off 120V AC? What kind of light output would I be looking at? What kind of cost would I be looking at?

TIA

 

[jtr1962]

Yes, Dave, I'm still following this thread. As to your question, driving LEDs directly off 120 VAC is fairly easy. You need a capacitor which functions as the reactive element to limit the current to the LED, a bridge rectifier, a filter capacitor, and a few other parts. You can easily make an LED nightlight, for example, based on this. That's the good news.

The bad news is that for home general lighting LED isn't quite there yet even though LED nightlights are appearing in larger numbers. To replace one of those Home Depot 23W 6500K CFLs you would need about 12 Lamina Ceramics arrays at a cost of ~$15 each or about 20 Luxeon IIIs at a cost of maybe $9 each. The cheapest near-term solution might be about 16 of Cree's newest power LED (available in maybe 6 months) at roughly $5 each. There are other problems as well. With the exception of the Crees, which are about 70 lm/W, all of the other LEDs are roughly 25 to 30 lm/W. Therefore, you would consume more than twice the power of the CFL, and more importantly you would need either a huge passive heat sink or a noisy fan-forced one to get rid of the heat. Besides all this, color consistency among LEDs, even of the same batch, leaves something to be desired.

LEDs are great for small and medium lighting needs. In fact, at this point I consider them the only real solution for lighting needs of a few hundred lumens or less. However, fluorescent still shines (no pun intended) for any lighting requirements over that.

I would say based on the current state of development (LED makers claim that they're two years closer to the holy grail of 150 lm/W than they thought they would be at this point) that perhaps in two or three years LED-based incandescent replacements will be hitting the store shelves, probably replacing the very inefficient candelabra-based bulbs first. At first they'll probably cost more than the CFLs. Within a few years they'll match the cost of CFLs and better them in efficiency. Probably by the early 2010s they'll cost not much more than incandescent light bulbs and have efficiencies of 120 to 150 lm/W. At about the same time incandescent bulbs will likely stop being made except for very niche uses.

Just be patient. You've got less than ten years before household LED bulbs are ubiquitous.

In the meantime, try some of these places for the bulbs you're looking for:

http://www.1000bulbs.com/
http://www.bulbs.com/default.asp?page=products
http://www.topbulb.com/find/default.asp

 

[ddrueding]

Thanks JTR, a very thorough and well formed answer.

 

[Stereodude]

Seoul Semiconductor is promising 100lm/W within the year. They have has 5W parts that will do 70lm/W when run at 1W right now. I've been playing with them at work and they sure are bright.

 

[LiamC]

According to this source, a "true" white LED has been developed. Not to sure about that claim but...

According to the Journal of the American Chemical Society, Michael Bowers stumbled across the true white LEDs after he was trying to make really small quantum dots, which are crystals generally only a few nanometres small.

Normally you get a bright colour when you shine light on quantum dots or apply electricity to them. But when Bowers shined a laser on his batch of dots he got a white glow instead of the blue he was expecting.

more here: http://www.theinquirer.net/?article=27158

 

[jtr1962]

I guess that depends on your definintion of what true white is. Now it's true that the spectrum of a white LED has peaks and valleys. Usually there is a peak right around 470 nm (that's the blue primary emitter), and another peak around 580 nm (that's the yellow phosphor). Combined the two give a white light which is slightly deficient in green and more deficient in deep red. Still, it's better a better quality white than the crappy halophosphor fluorescent tubes which were used everywhere for years until triphosphor tubes started replacing them in the 1980s and 1990s.

Maybe the spectrum from these quantum dots is smoother than that of regular blue+phosphor LEDs although if it is yellowish-white as the article says I can hardly call it true white. I'd guess though with a little tweaking we could get something close to the sun and that in my mind would be great for interior lighting. I always thought incandescent bulbs were just too "warm". Purples and deep blues just drop out, greens are faded, and reds are too intense. Why you would want an LED to imitate such poor lighting is beyond me. I remember getting plenty of eyestrain when I had to read by incandescent bulbs when I was a kid. Even those horrible aforementioned old-school cool-white fluorescent tubes were better.

BTW, "regular" white LEDs come in all shades. I have some that give an incandescent yellowish-white light, others which are fairly close to the 5000K fluorescents which I use almost everywhere now (these are close to "true" white), and still others which give varying amounts of bluish-white light (some are admittedly horribly blue).

 

[LiamC]

BTW, "regular" white LEDs come in all shades. I have some that give an incandescent yellowish-white light, others which are fairly close to the 5000K fluorescents which I use almost everywhere now (these are close to "true" white), and still others which give varying amounts of bluish-white light (some are admittedly horribly blue).

I think I have commented on this before--I'm the opposite. I find most flouro's too "cold", and with the blueish ones, I find the cold light lacks a significant amount of contrast to my eyes--to the point I find it difficult to focus--and this with a 100W compact flourescent versus a 75W incandescent. Warm white flouro's I find much better, but not as good.

In fact the best lights in my house are in the bathroom, the 4 x 575 infra-red lamps