LED light output

But it's not really white light. LEDs give off orange light, with a narrow deep blue frequency peak added in. It appears to your eye like white light, but it really isn't. (much like how your computer screen does not actually give off any yellow light, but when red and green pixels are mixed it appears yellow to your eye)

Furthermore, because of the particular deep blue frequency in LEDs, it is harder for the human eye to focus on. So your patients are not going to be seeing better. Ever look at a blue-colored light store sign at night? Notice how it looks a little blury?

And then there is color rendering. A light source can't really illuminate an object if the specific frequency of the light is not the same as the frequencies reflected by the object. Look at a red colored object in blue light and it will just look black. Basically, LED light will only illuminate the range of colors from reddish orange to greenish yellow. When it comes to the blue part of the spectrum it is like black and white color rendering, so to speak. Reds and blue-greens will appear somewhat greyish. If you do not believe me, take a red rose (with stem and green leaves still attached) in a darkened room. First, look at it under incandescent light. Then look at it under LED light.

Saying the phasing out incandescent is not so bad because LEDs are so much better assumes two things: First, you make the assumption that LEDs actually are better, and second you assume that ignorant penny-pinching consumers will not just reluctantly switch over to CFLs, not realizing the disadvantages.

 

another article I found:

 

Apparently even some LED bulbs can pose a fire hazard:
http://www.geek.com/articles/gadget...00-led-bulbs-because-of-fire-hazard-20130320/

(though the fire hazard risk of LEDs is still much smaller than CFLs)


I am making all these posts because, so often, in arguments when I try to convince people that CFLs have severe disadvantages, and the light bulb phase out was a stupid idea, they just completely dismiss it and say something like "oh, well LEDs are the future", even though relatively few consumers have actually tried LED lighting in their homes yet, so all the potential disadvantages may not be known.

 

They are now making dimmable LED bulbs. One problem: the light has high frequency flicker when the bulbs are dimmed. This is the same type of flicker that many people have long been complaining about fluorescent lights. To most people, it is not consciously discernible. But it can contribute to eye strain, and may both certain sensitive people, especially those prone to migraines, epilepsy, or those with autism.

You see, instead of actually dimming the LED chips, they are simply switched on and off very fast many times per second because the LED chip does not evenly dim if the power was just simply reduced.

 

I wish more research was being done into electroluminescent technology. Most people are probably familiar with them in special night lights and in some watches:



http://www.rainydaymagazine.com/RDM2010/RainyDaySports/TimexExpedition/FirstLook/IndigloBig.jpg

Electrolumiscent technology can give off a much softer white light than LED can. The type of phosphors in electrolumiscent panels give off a broader hump of frequencies, and the range of possible phosphors is greater. With white LEDs, in contrast, there is a very narrow blue frequency spike, and essentially only one type of LED phosphor has been developed so far, which although it gives off a very broad hump of frequencies, it does not cover all of the spectrum. Narrow frequency spikes appear to the human eye to be more harsh, while broad humps in the spectrum appear more soft. This is regardless of color. This probably has to do with the slightly different refraction of different frequencies in the human eye causing trouble focusing.

Unfortunately, electroluminescent technology at this time does not give off enough light for anything more than decorative purposes.



http://electroluminescence-inc.com/howtouseEL.htm

Large panels are expensive, and while they have long lifetimes, the brightness quickly fades within a year if run at maximum power.

Probably the REAL reason there has not been as much investigation into them is because, despite the better light, their efficiencies are lower than LED. Reasearchers believe that the efficiencies of electrolumiscent panels can be greatly increased with further advances in technology, but not to the point of LEDs. Since all the hype seems to be on "environmental sustainability" and not on actual quality of light, I am not sure how much chance electrolumiscent technology has with all the research being focused on LED.

Seems like they expect everyone to sacrifice quality of light for the sake of efficiency.

 

The light from latest LED lamps coming to market are getting better, though the new ones are significantly more expensive.

I am normally really good at differentiating between the light from LED and halogen. It is usually fairly obvious to me. I have seen LED PAR lamps in many stores now, and it has always looked off. The light is simultaneously pinkish, purplish-blue, and unnaturally yellowish in a strange sort of way, and it always makes the colors in a room look kind of greyish. It lacks that deep orange warmth of incandescent.

So I went to the Starbucks coffee, and was looking at the display shelf, and noticed the warm glow. Now this was surprising because I had been there before and remembered that they had LED. It had just not looked right. And now they switched back to halogen?

I took a closer look at the lighting and saw that it was really LED after all! MR16 shaped spotlights throughout the store. I do not think they had red frequency chips inside them, because the MR16 lamps each had 3 point-like lightsources, non-diffused. So apparently these new MR16 LED have a different phosphor composition, with red frequency coverage in the spectrum. I think I had read about these new LEDs, but was surprised to see them already in use in an actual store.

My observations are confirmed by this I found on Starbuck's website:

After I realized it was LED, I was able to see that the light was not exactly the same as how halogen would have been (there was still that pinkish/magenta color). But these new LEDs did have that "warm" feeling one would expect from an incandescent source. And this is what the coffee shop needed, what the previous LED lighting could not provide.

The whole store was filled with these MR16 lamps. Two of them towards the back where the employees work had apparently not been switched out yet, still the old regular LED, the difference in light between them was clear.

Most normal people do not notice these subtle things, but when one is a lighting fanatic... But it really does make a difference, it sets a different atmosphere.

This experience got me to go buy and test out the latest Osram-Sylvania Professional Series retrofit directional lighting. This is not your typical LED bulb. Supposedly it has a 95 CRI rating, though this is not indicated on the packaging. It uses standard blue chip LED, but apparently the phosphor composition is adjusted to give it more coverage in the red frequency part of the spectrum. I must say I am impressed. One could easily mistake it for halogen flood light. On closer inspection, the light quality is slightly different. I would not say it is better or worse than halogen, though. At 3000K CCT, the light from this LED lamp is "sharp", feels like "high-definition", and really brings out the reds. The light has more of a "creamy" overall color. In contrast, halogen light seems more soft and dull by comparison. There was an interesting difference in color rendering also. Though both halogen and this LED made skin tones appear good, there was a noticeable difference. It is a bit difficult to describe. It almost seemed that this LED brought out the reds even more than halogen. I had a little cut on my finger and the LED made the red appear almost fluorescent, it really stood out. It looked more dull and brownish under halogen. For illuminating the colors of wood, I honestly could not see a difference between the two.

So at this stage, I would have to say that there is not really any reason for most commercial stores to switch their halogen spotlights out with high CRI LED. Perhaps if it is a really high end store and most of the merchandise being displayed has deep green colors, for example at an orchid exhibition (being shown at night) or something like that (okay yes, I realize this is a little implausible ). The quality of light from the Professional Series LED is clearly superior to standard LED. In commercial situations, the lights are being left on all the time, and the cost of continually replacing burnt out halogen spotlights can add up fast over a few years. Another advantage here is that if one wants whiter light, 3500K is easily available from LED. While 3000-3500K halogen is available, they generally have shorter lifespans, 6 months to a year (the hoter the filament, the faster it burns out). In contrast, the LED can basically last forever.

As for the improvement in phosphor, I am sure they most likely have adjusted the phosphor composition to cover more into the green as well, to balance out the overall color because of the red. Again, the light was more of a creamy color, not really pink. The lack of broad spectrum coverage in the blue probably does not matter as much because the CCT is only at 3000K. At higher CCT, I am sure that becomes more important to quality of light. And like I mentioned, to adjust the phosphor to give more green coverage, a small amount of this increase is likely also spilling over into the blue, so that probably helps.

It should be mentioned that these new LED lamps are more expensive, for technical reasons I will not both getting into. Because of the high initial price, they will not make sense in all situations.
(The 90-watt equivalent Professional Series flood lamp costs 65 dollars each! )

 

When we remodeled our bathroom almost 20 years ago, I put in two, 10 bulb fixtures, running 60W bulbs. No need (and no power for) a bathroom heater. 10 years ago, I replaced the 60W bulbs with CCFL's. The first time I turned on the lights, I felt cold. My brain associated the light with heat - which the CCFL's lack.

LED's are getting much better, and with volume will continue to do so. The do have the same problem as CCFL's, they depend on the phosphor for color. (and, quality control sucks, I usually buy twice the CCFL's I need to get reasonable color match).

I have tried several lighting fixtures under the kitchen cabinets - what has worked best is LED's on tape (Ebay, $16 for 5 meters + $20 for a 12V power supply). They will work fine even with a few failures (none in the 6 months they have been on).

The other problem with LED's is their efficiency falls pretty fast with temperature. Fixtures designed for LED's are better than bulbs that fit into existing fixtures (especially the can lights - they eat my CCFL's as fast as they eat incandescent bulbs).

 

Seems to me that reflecting and refracting the light source is equally critical to the light source itself...I think this is where the magic will come from...

 

Actually, this may not be the case in the future. Soraa has developed "GaN on GaN" technology that allows LED chips to withstand higher temperatures during operation. Still not oven temperatures, but hot enough to reduce the size of the heat sink.