The future of lighting is not yet here

Miscellaneous and Personal Stuff I Must Share
1

The other day, on a whim, I ordered myself an LED light bulb. Seduced by the claim that I could get a one-watt light bulb, I decided to take a flyer on it – said flyer costing me about $35 with shipping. The package came yesterday, and with some fond anticipation of entering the future of lighting, I screwed my new bulb into the fixture over the sink.

The future only lasted the three seconds it took me to cross the floor and flip the light switch. Unless, of course, I’m wrong about the future, and it will after all be illuminated by feeble beams of ghastly bluish-white light.

The crazy thing to me is that designers have gone to great trouble to configure these LED lights so you can swap them out in ordinary light fixtures – but they don’t seem to have gone to any trouble to recreate the one great thing about incandescents: the quality of the light. I think for most people, that’s what they want their light to look like. The biggest complaint about compact fluorescents is that the quality of light compares poorly with that of incandescents. And yet, compact fluorescents have a quality of light that’s about a hundred times as good as that of LEDs.

I want my $35 back!

2

The quest for the perfect white light LED continues. A white LED bulb is a blue LED with a phosphor that glows yellow - a trick of the eye makes that look white, but when it reflects off a surface, the spectral inadequacies show up. For that sort of money, though, why did they not use tri-leds (red/green/blue LEDs with a diffuser to give white - I’d be happy with 3 Watts).

The holy grail of research in this area is a high efficiency UV led, wrapped with UV activated phosphors that glow red, green and blue, and a really good UV-filtering clear lens.

Or maybe quantum dots.

Si

3

In fact, the package insert says the bulb uses 3+ watts. The website, on the other hand, says one watt.

4

Actually, on this point – do we want perfect white light? Incandescent light is distinctly yellowish, but pleasantly so. Maybe because the bulbs remind us of the sun that way?

5

Did the documentation say what LED emitter was used, Luxeon (1, 3, 5, or Rebel?), Cree (XR-E?) or Seoul Semiconductor (P-series), or is it an older 5MM/10MM package

LED’s as stated upthread are simply a blue emitter coated with a yellow phospor, and they have a large deficiency in the red/orange/yellow bands, the light has a very strong blue spike, and blue light scatters very easily on the human retina

incandescent bulbs are similarly deficient in the blue spectrum, but have a much more balanced color balance than LED

the best way to impove the color rendering index of an LED is to take the standard high-power LED emitter, and add a small 5MM red emitter to it, it kicks in just enough red light to improve the power-LED’s CRI, still not a match for a well driven incandescent though, human vision is adapted more to the Incan spectrum

look at any high-end flashlight (SureFire’s incandescent line, like the 6P/G2/9P/G3 series) and see what a nice, hard-driven incan bulb looks like, don’t bother suggesting maglites, in stock form, they’re utterly pathetic, but the make great modding hosts

so, to get back on track here, the bluish light emitted from your LED lightbulb is normal, using a single emitter in a household fixture doesn’t help much either, put in a cluster of Luxeon Rebels, and you could get a passably decent LED bulb (the Rebel has the warmest tint of the current Power-LED’s)

6

I was going through my iDisk, and found some good example photos of the difference between LED and Incan in flashlights;

first pic, a SureFire E1L modified with a 90 lumen Seoul Semiconductor P4 LED vs. a 75 lumen incan SureFire A2 Aviator;
E1L on the left, A2 on the right
the same E1L Vs. a 120 lumen incan SureFire P61 lamp in a 6P;

now, some distance pics
E1L;
A2;

Skintone rendering tests;
Baseline with flash;
Seoul Semiconductor P4 (SF E1L)
SureFire A2 Incan;

7

Mods. can you add this last line to my previous post, thanks, i forgot to include the Luxeon Rebel, as it’s the most incan-ish LED;
Luxeon Rebel (80 lumens)

8

According to the LED Museum, you can get LEDs in a squillion different colours. Why not use one of each, so to speak, in one of those 16-LED lamps?

9

MacTech, thanks for those demonstrations. Best-case scenario (your last link), the light makes your fleshtones look like you’ve been drowned and fished out after only a day, rather than a week.

10

>According to the LED Museum, you can get LEDs in a squillion different colours. Why not use one of each, so to speak, in one of those 16-LED lamps?

Broadly speaking, there are two efforts in LED illumination - making phosphor based systems with blue or UV LEDs, and combining multiple LED emissions as you suggest. I got interested in LED illumination and got 1 W and 3 W standard base bulbs to play with, one’s in front of me now. As I looked around I noticed that the phosphor based approach seems to be the one used in all the commercial offerings.

If you buy multiple color LED Christmas Tree light strings, they will give you a good idea of what the other approach can look like. Of course, you also have to balance the colors, so if it’s too red you buy more greenish and bluish colors and if it’s too purple you buy more greens, and so forth.

11

Yeah, the Seoul P4 is the worst of the bunch for rendering my pasty-white skintone

here’s the full set;
Baseline
Cree XR-E
Luxeon III
Luxeon Rebel
Seoul P4
A2 Aviator (Incan)

from best to worst it goes;
Baseline Flash
A2
Rebel 80
Cree XR-E
Luxeon III
Seoul P4

12

The efficiency varies a lot by color. Many years ago, I designed a specialized macro attachment for a digicam. It needed an on-axis Illuminater, which I accomplished with red, green, and blue LED’s. (white LED’s were still a few years in the future) I used one blue, two red, and 6 green LED’s of the highest efficiency (the green) I could find. The light still had a strong magenta cast. (not enough green) It was good enough for the application, though, so we went with it.

Another problem with this approach pops up when the coverage of each color doesn’t match up. You get colored halos in the shadows. In the application mentioned above, this made edges really pop out, which was desireable.

13

Sal it looks like most of their lights are of the older 5MM emitter technology, most likely Nichia CS or DS LED’s, and most of those lights are of the multi-LED “Showerhead” technology, a cluster of 5MM LED’s

the good news; 5MM package LED’s are incredibly efficient
the bad news; 5MM LED’s are generally even bluer than the “Power LED” technology (Luxeons, Crees, Seouls)
the bad news; “Showerhead” lightbulbs are fairly simple, and use a step-down regulator to drop the light socket voltage to something the 5MM’s can handle, but even then, the 5MM’s are invariably overdriven, and have a short lifespan, you may start losing individual emitters on a gradual basis

here’s a 5MM LED flashlight in a hallway;
Inova X1
and a Luxeon 1 watt LED;
Fenix L1P
notice the difference in color balance?

14

MacTech, I guess I’m paying for my ignorance here. This is what happens when you buy without doing any research. I naively assumed that all LED bulbs would be more or less than same, sort of the way incandescents of the same type give the same sort of light and brightness regarless of brand.

The example you give in the post above is pretty compelling.