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Author Topic: Tricked by new LED, thought it was halogen for a minute  (Read 4881 times)

Offline Anders Hoveland

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  • Posts: 21
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:
Quote
LED bulbs have come a long way and we?ve been able to find some that provide the quality of light we needed in our stores ? warm, inviting, and makes the coffee look even more delicious, and our customers even more beautiful. We did this by reaching out to GE, who developed a highly energy-efficient LED bulb that complements Starbucks store design approach and fits existing fixtures.  


Does anyone know what they might be?

 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.



http://www.youtube.com/watch?v=FCriVHQOFFE

 I just tested the Osram-Sylvania Professional Series retrofit PAR lighting. 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 PAR. 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.

 Coincidentally, I bought this LED PAR to replace a neodymium glass halogen PAR that had burnt out. Really, the light from the two are quite comparable. It is in a location that gets left on all the time. The halogen PAR was rated at 2000 hours and 3000K. That is probably why it was designed with neodymium glass, to filter to a slightly higher color temperature than would otherwise have been possible. Without the filter, the filament would have had to be hotter to reach 3000K, and then the lifespan would have been only half that. Unfortunately the bulb was rather expensive (to be expected with a neodymium glass halogen PAR lamp). Since it burned out after only 6 months, it just made sense to try the new high-CRI LED. The Professional Series LED was quite expensive, but only 3 times more than the expensive bulb I had before. The light from the new LED lamp is very much like the neodymium filtered halogen in that they both have a "creamier" color of light, and the light from both feels a little "higher definition" than normal halogen PAR. I realize that the spectrums are different, but just commenting that the overall effect seems quite similar.

 I also tested the color rendering on greens and turquoise colors. Some of the green paper I was using was a fluorescent lime green, and glowed more brilliantly under the LED than the halogen (not surprising). The LED still made greens appear a little off (similar to fluorescent light). The color rendering for blue-greens was better than normal LED, but still not as good as halogen. And different turquoise colored objects that appeared similar under halogen and daylight looked appeared different under the LED. Also for blues, the Professional Series brightly illuminated the blues (much more so than halogen), but it also made them appear a little weird, just slightly "off", it is difficult to describe. Overall, most of these observations are consistent with what one would expect.

 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 3500K halogen (slightly tinted reflector if you were wondering) is available, they have an impractically short lifespan for commercial applications (the hoter the filament, the faster it burns out).

 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.

(The efficiency of my Professional Series PAR lamp is 55 lumens per watt, if you were wondering, about the same as most lower cost LED retrofit bulbs)
« Last Edit: May 30, 2013, 06:00:30 pm by Anders Hoveland »