# Finding true cyan LEDs



## saabluster

I just had a theory that I thought I pass by the crew here. I honestly haven't put much time into it to figure out whether or not I am off my rocker here or not but here goes. It's been a bit slow around here anyways.

I know many of you have been looking for true cyan emitters and they seem incredibly rare to say the least. I ordered some "cyan" rebels a while back and they were straight green. I was ticked off they can get away selling those as cyan. One thing that occurred to me was how the farther you move away from green the lower the lumen output of the LEDs generally are. The "cyan" LEDs I bought were the highest flux bin I could buy. In thinking about it I wonder if that would mean it is more likely to be at the green end of things. Maybe if I ordered low flux bin cyans I would be more likely to get a true cyan. Since none of the places I have seen allow you to buy based on the binning of the wavelength maybe this is a way to know without knowing. What ya think?


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## JohnR66

I'm not sure if your theory would work. Did the seller specify the dominate wavelength? At least with low powered LEDs, I notice the cyan ones tend to shift more green unless driven at full current.

I see SuperbrightLEDs has a cyan Cree X lamp rated 505nm. Their prices may not be the best, but they are a possible source for power cyan.


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## HarryN

The "cyan" that is sold by nearly everyone is targeted at US traffic light "green", which is nominally 505nm. This used to be quite difficult to make "bright",but there is a lot of demand, so it gets development attention.

IIRC, there is a slightly bluer color used in Japan in traffic lights, or at least used to be? Perhaps Nichia has a product like that.

Sometimes, you can ask Future to find a specific color bin for you. We are all used to paying attention to white LED color space, but there is also a similar binning for color LEDs. It used to be easier to obtain these "non central" color spreads, but with improved process control, the production has gotten much tighter. Now you might have to buy a reel or more.

IMHO, there are some big holes in the standard LED color offerings at around 490nm and between "green" and "amber". (sort of like yellow) 

There are a few companies that make LEDs in that range. Osram might have a version as they have a lot of options. Otherwise, it takes lots of searching.


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## saabluster

JohnR66 said:


> I'm not sure if your theory would work. Did the seller specify the dominate wavelength?


I speak of Future Elec. I tried looking for cyan and I don't see where they have the cyan grouped into bins for wavelength. On Cutters site you can get the greens for instance binned very tightly. If only Cree still made cyan LEDs.



HarryN said:


> The "cyan" that is sold by nearly everyone is targeted at US traffic light "green", which is nominally 505nm. This used to be quite difficult to make "bright",but there is a lot of demand, so it gets development attention.
> 
> IIRC, there is a slightly bluer color used in Japan in traffic lights, or at least used to be? Perhaps Nichia has a product like that.
> 
> Sometimes, you can ask Future to find a specific color bin for you. We are all used to paying attention to white LED color space, but there is also a similar binning for color LEDs. It used to be easier to obtain these "non central" color spreads, but with improved process control, the production has gotten much tighter. Now you might have to buy a reel or more.
> 
> IMHO, there are some big holes in the standard LED color offerings at around 490nm and between "green" and "amber". (sort of like yellow)
> 
> There are a few companies that make LEDs in that range. Osram might have a version as they have a lot of options. Otherwise, it takes lots of searching.


505 is still in the green spectrum though. I also don't have the buying power to order full reels to get the bin I want. I'll look at Osrams offerings. Thanks.


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## blasterman

What specific wavelength are you looking for? 

'Cyan' to my eyes pretty much describes any cheap Cree 'blue' emitter. I've had some Lux IIIs even worse. Perhaps looking for blue bins with the longest possible wavelength would work.


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## netprince

Just a quick search on cyan leds shows they are the most visible to the eye? Is that why they are desired?

Just curious, if you search XREBLU-L1-R250-00K01CT-ND on digikey, does it look promising?


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## saabluster

netprince said:


> Just a quick search on cyan leds shows they are the most visible to the eye? Is that why they are desired?
> 
> Just curious, if you search XREBLU-L1-R250-00K01CT-ND on digikey, does it look promising?


That looks very promising. Thanks!


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## blasterman

Nice job Netprince!


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## JohnR66

netprince said:


> Just a quick search on cyan leds shows they are the most visible to the eye? Is that why they are desired?
> 
> Just curious, if you search XREBLU-L1-R250-00K01CT-ND on digikey, does it look promising?



These will be too blue to me. Certainly not royal blue, but not really cyan either. Sounds like he needs something in the 490-500nm range if the "traffic light" green is too far into green. This odd tint may be tough to find. Better to mix two LEDs if application allows.


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## 2009Prius

JohnR66 said:


> ... This odd tint may be tough to find. Better to mix two LEDs if application allows.



+1. blue + green --> cyan

Good luck!


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## blasterman

Mixing blue and green LEDs will result in dull saturation and other color problems. I have fully mixable RGB PARs, and trust me, running up the blue and green yields a muddy 'cyan' at best.

The LEDs linked above are 485nm, and this is close to the ideal where most tech sheets put true cyan. However, there's a lot of subjectivity involved as to what is actually preferred here. In any case, using a specific emitter with desired spectral peak is a much better than mixing.


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## saabluster

blasterman said:


> Mixing blue and green LEDs will result in dull saturation and other color problems. I have fully mixable RGB PARs, and trust me, running up the blue and green yields a muddy 'cyan' at best.
> 
> The LEDs linked above are 485nm, and this is close to the ideal where most tech sheets put true cyan. However, there's a lot of subjectivity involved as to what is actually preferred here. In any case, using a specific emitter with desired spectral peak is a much better than mixing.


Agreed. Mixing two colors does not make them combine into a spectral output in the middle. It's not the same. Well I put through an order but for the XP-E version with the same code as they were actually in stock. I will let everyone know what comes of it when they arrive.


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## Bullzeyebill

Seems that Luxeon had some nice Lux V cyan's several years ago. Just did some googling for Cyan pics, and mostly nil, either pics not showing up, or dead Photobucket. Here is a post with various colored LED Arc's, with some cyan shown. I suspect these are Luxeon's. Whoops, looks like some 5mm colors too.

Bill


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## netprince

What would you guys recommend as a good host for one of these? I was thinking a jetbeam rrt0 would be nice, but its a little bit spendy. Easy to swap the emitter though...

I ordered two emitters also, looking forward to trying out cyan...


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## netprince

I found this to be an interesting read related to the subject...

http://www.visualexpert.com/Resources/nightvision.html



> As illumination declines, the visual system starts conserving light in three ways. First, inhibitory responses weaken, and eventually stop. Second, inhibition is replaced by convergence, where the receptor outputs sum together to increase sensitivity but further reduce resolution. Third, there is more available photopigment as light declines. When light strikes a molecule in a photoreceptor, it "bleaches" the molecule, causing electrical activation that leads to a visual sensation. While in the bleached state, it is unresponsive to light. The more photopigment in a bleached state, the less available to respond to light and the lower the sensitivity. In dim light, very little of the photopigment is bleached, so the eye has greater light sensitivity. All of this occurs before and continues after the switch from cones to rods.
> 
> One effect of switching to rods, however, is the "Purkinje shift." During photopic cones vision, viewers are most sensitive to light that appears greenish-yellow. In scotopic vision, they are most sensitive to light which would appear greenish-blue during the day. (Of course, viewers can't actually see color in scotopic vision. It is incorrect to say that "people are most sensitive to blue light at night.") One main result of switching to rods is loss of most sensitivity to long wavelength colors (red).


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## saabluster

Well I now have the emitter and it is more blue than cyan. At very low currents it is almost a perfect cyan but turns more blue as the current increases. The search continues.


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## netprince

What was the digikey part number you ordered?


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## saabluster

netprince said:


> What was the digikey part number you ordered?


XPEBLU-L1-R250-00Y01CT-ND


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## HarryN

posting error


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## nailbender

Hi 

Wayne at the shoppe had some lux5 cyan emitters not long ago. 

Cutter has some Cyan Cree XR on sale right now under special sale. 

Dave


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## netprince

Just got my XREBLU-L1-R250-00K01CT-ND and powered one up, really blue. Not green-blue like the other images hanging around on CPF...


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## netprince

Just an update...

I got out my quark RGB, started comparing them in a dark room, and interestingly the XREBLU-L1-R250-00K01CT-ND does appear to be about midway between the green and blue on the quark. 

The quark's blue LED is very 'dark blue' (not sure the right term). The XREBLU-L1-R250-00K01CT-ND by itself looks blue, but when comparing it to the quark, it does look much greener.

I tried taking a picture to show the difference, but my camera doesn't seem to pick up the colors correctly... strange...


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## saabluster

Well thanks for the suggestions guys. I am curious if anyone has seen a significant improvement by adding cyan/green. Personally I just don't think it is worth the extra energy draw. Other than balancing out some excess red in the beam I don't see what it is good for as I didn't see that much improvement in the way the leaves look outdoors. :shrug:


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## 2009Prius

netprince said:


> ...
> 
> I tried taking a picture to show the difference, but my camera doesn't seem to pick up the colors correctly... strange...



You may try turning off the auto white balance or including a white background in the field of view.


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## 2009Prius

blasterman said:


> Mixing blue and green LEDs will result in dull saturation and other color problems. I have fully mixable RGB PARs, and trust me, running up the blue and green yields a muddy 'cyan' at best.
> 
> ...



Sounds like the spectra of at least one of the LEDs in the mixture is "dirty" to start with. Too bad...


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## 2009Prius

saabluster said:


> Agreed. Mixing two colors does not make them combine into a spectral output in the middle. It's not the same. ...



Many different spectra may be perceived as the same color by the human eye, which has only 3 types of receptors (some women have 4 the rumor says).


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## netprince

Another possible use, treatment of SAD...

http://en.wikipedia.org/wiki/Seasonal_affective_disorder#Treatment


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## thepaan

saabluster said:


> Well I now have the emitter and it is more blue than cyan. At very low currents it is almost a perfect cyan but turns more blue as the current increases. The search continues.


 
Blue LEDs shift towards UV with an increase in current but shift towards IR with an increase in heat. The shift shouldn't be greater than a couple nm so I'm surprised you notice it at all. I realize a high temp also shortens the life of the product but you could try not using an overly adequate heatsink - lets say one that allowed the LED to get up to say 50 or 60*C. Just a stab in the dark here....


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## IsaacHayes

You used to be able to get true cyan cyan luxeons, but now they are all traffic green. You all are on the right path to go for a blue luxeon that is binned very high towards green. 485nm is perfect.

I have a lux3 driven at 1 amp and it's perfect. Took me MANY tries to get what I wanted... My ISP deleted my subfolders on my website, and I can't find the original mod pics.  big time upset about that, man this sucks.

When driven harder, it will go bluer. If you let it get hot, it will go green. Mine is cooled well and ran at 1 amp (dual BB500's, on 2 NiMH C). I ran dual BB500's as 1 set at 1amp would exceed the input current limit of the board, since the input voltage is quite low. By having 2 they share the load and it works great.


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## anuragwap

I resurrected this old thread since I've found a cheap source of true cyan emitters. Well,not quite. But they are in 495-500nm (bin2 cyan) range. These are the so called 'Exotic LEDs' available through LEDGroupBuy.com. Comparing side by side to my (dull) bin3 cyan Lux-V, I am now sure that these are indeed 495-500nm dominant at 700mA.

The other reliable option is ordering 1000+ cyan rebels from Luxeonstar, which is silly. Nichia/Avago has refused to accept bin specific order for high powered cyan LEDs even if ordered in full reel.

Another option, not very well known is using very low efficiency 1W emitters (490nm peak) from Epitex, a Japanese LED chip manufacturer. These are available from Roithner Lasertechnik/Marubeni America at ridiculously high prices/MOQ.

There's a Hong-Kong based company called YesLed which seems to manufacture (maybe in the past, probably didn't update their catalog) 485-495nm led dice, but no emitters.

I made a shower-head arrangement of 5mm LEDs with 217 rank C (495-500nm) NSPE510DS LEDs, resulting severe back pain after soldering the leads! I overdrive the cluster to 2.5-3A(for short time) to get a decent (bin1 equivalent) cyan.


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## blasterman

Steve's LED's sells a 'Cool Blue' Rebel ES that specs between 470-480, but to my eyeballs is no less than 480nm. They are pretty green.

Thought about using them to build an insanely high CRI room light.


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## anuragwap

Ordered 1 cyan and 1 cool blue from StevesLED.

UPDATE: Bad luck, their cyan is ugly bin4, and their sky blue is too blue for me, only a bit lighter than the common blue Cree c503 leds. To make up for my loss, I decided to mix them by wiring in series. The result was a nicely saturated greenish blue. Maybe I should mix more cyan's with fewer sky blue's to get a balanced cyan.


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## PhotonFanatic

Cyan emitters--I've still got some of the best that Future ever made-although they were Lux Is. 

But when driven at 750mA, they are very bright and just the most beautiful color cyan you could want.

Yeah, that drive current was suggested to me by someone at Future--he said that while the lifetime would drop, it still would be close to 5,000 hours.


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## Canuke

anuragwap said:


> UPDATE: Bad luck, their cyan is ugly bin4, and their sky blue is too blue for me, only a bit lighter than the common blue Cree c503 leds. To make up for my loss, I decided to mix them by wiring in series. The result was a nicely saturated greenish blue. Maybe I should mix more cyan's with fewer sky blue's to get a balanced cyan.



That's the best way to get the hue you want: mix readily-available wavelengths that are as close to the target hue as possible.

You won't get good cyan by mixing "standard" RGB colors, where green is around 520nm and blue at 460nm. Because of the green, that "side" of the RGB triangle leaves a large "lobe" of the color space outside its gamut; the closest approximation is significantly closer to the central white spot, i.e. there's not a lot of saturation. Cyan is actually the one hue that sRGB is least capable of rendering to high saturation.

Morevoer, the human eye is most sensitive to hue changes in this part of the spectrum. Look at the CIE curve; the evenly spaced wavelength markers are more spread out in that area than anywhere else on the curve. This is why shifts in hue are so much more apparent with emitters in this part of the band versus anywhere else; you won't notice a +/-3nm shift in a 650nm red emitter, but you will on a 488nm one. I'll bet that this effect is why there can be significant subjective variations between two people looking at monochrome cyan lights over what color they think it is, exactly. If you are looking for the "perfect" hue, you can most inexpensively dial it in this way.


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## HarryN

I think what you want is what used to be called blue bin 6. Not sure if that is still correct or not, but in that 485 - 490 nm range IIRC. The challenge is that it is easy to shift 2nm just from warming up, and that is a big shift at that color point. Try some of Photon Fanatic's Lux Is, you might be surprised how great they are.


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## saabluster

Thanks for the input in this thread all. I ended up finding what I wanted though. Avago has a cyan LED that I tested in a spectroradiometer. They were a beautiful cyan color. Here is the raw data.

Yellow marks the wavelength peak. Part #ASMT-JC11-NST01


4001.142359E-0124011.305785E-0124021.491367E-0124031.707347E-0124041.949249E-0124052.21931E-0124062.515304E-0124072.832124E-0124083.158338E-0124093.538965E-0124103.903881E-0124114.268018E-0124124.641073E-0124134.998526E-0124145.348253E-0124155.676182E-0124165.996254E-0124176.30795E-0124186.608934E-0124196.905123E-0124207.189547E-0124217.478814E-0124227.760703E-0124238.050214E-0124248.338784E-0124258.63379E-0124268.935095E-0124279.245154E-0124289.567313E-0124299.907047E-0124301.026704E-0114311.065986E-0114321.106232E-0114331.151091E-0114341.197769E-0114351.250794E-0114361.311093E-0114371.37523E-0114381.447858E-0114391.528843E-0114401.621297E-0114411.724605E-0114421.840214E-0114431.972687E-0114442.12604E-0114452.296123E-0114462.490797E-0114472.714644E-0114482.971325E-0114493.257676E-0114503.580618E-0114513.959661E-0114524.377275E-0114534.849156E-0114545.376556E-0114556.002702E-0114566.704541E-0114577.469629E-0114588.350367E-0114599.34287E-0114601.046154E-0104611.17734E-0104621.321538E-0104631.482368E-0104641.662912E-0104651.870685E-0104662.100172E-0104672.352093E-0104682.633782E-0104692.936946E-0104703.270859E-0104713.650551E-0104724.065765E-0104734.536724E-0104745.087646E-0104755.700618E-0104766.385797E-0104777.18277E-0104788.056805E-0104798.982055E-0104800.0000000014811.108051E-0094821.218877E-0094831.339101E-0094841.455233E-0094851.57962E-0094861.702691E-0094871.827023E-0094881.944522E-0094892.056536E-0094902.163176E-0094912.252263E-0094922.331879E-0094932.393029E-0094942.438189E-0094952.46402E-0094962.470807E-0094972.459249E-0094982.430368E-0094992.385704E-0095002.327053E-0095012.25551E-0095022.177913E-0095032.091755E-0095040.0000000025051.906136E-0095061.808378E-0095071.713306E-0095081.620935E-0095091.528111E-0095101.440092E-0095111.353841E-0095121.270531E-0095131.195086E-0095141.122061E-0095151.053664E-0095160.0000000015179.248806E-0105188.658131E-0105198.133777E-0105207.606843E-0105217.120525E-0105226.638793E-0105236.182568E-0105245.756395E-0105255.355418E-0105264.973734E-0105274.613203E-0105284.286159E-0105293.969579E-0105303.676203E-0105313.404806E-0105323.15927E-0105332.947597E-0105342.7322E-0105352.534005E-0105362.355758E-0105372.192256E-0105382.037059E-0105391.892112E-0105401.756544E-0105411.629717E-0105421.51238E-0105431.399529E-0105441.293977E-0105451.194971E-0105461.101403E-0105471.018992E-0105489.401337E-0115498.669414E-0115508.009427E-0115517.404531E-0115526.857022E-0115536.343328E-0115545.879982E-0115555.444538E-0115565.04516E-0115574.67068E-0115584.330378E-0115594.011693E-0115603.714329E-0115613.437823E-0115623.173883E-0115632.940898E-0115642.723758E-0115652.521905E-0115662.336279E-0115672.16593E-0115682.002472E-0115691.857551E-0115701.728397E-0115711.606538E-0115721.492689E-0115731.38695E-0115741.28975E-0115751.198574E-0115761.114145E-0115771.033596E-0115789.609101E-0125798.931806E-0125808.308541E-0125817.740564E-0125827.210307E-0125836.707014E-0125846.256915E-0125855.843098E-0125865.457412E-0125875.09004E-0125884.77324E-0125894.474127E-0125904.193354E-0125913.930163E-0125923.693058E-0125933.468128E-0125943.25378E-0125953.059763E-0125962.873207E-0125972.706775E-0125982.546376E-0125992.4019E-0126002.264691E-012


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## BVH

Are these your "To Die For" Cyans? I bought a bunch from you waaayyyyy back when and still have them in my parts bins. I had one put in a Fenix pocket light and I have 4 in Mac's 4-Cyan, green cut down mag beauty! Eight power levels up to 1 Amp. Beautiful Cyan color!

http://www.candlepowerforums.com/vb/showthread.php?146752-Quad-Cyan-*SOLD*&highlight=quad+cyan



PhotonFanatic said:


> Cyan emitters--I've still got some of the best that Future ever made-although they were Lux Is.
> 
> But when driven at 750mA, they are very bright and just the most beautiful color cyan you could want.
> 
> Yeah, that drive current was suggested to me by someone at Future--he said that while the lifetime would drop, it still would be close to 5,000 hours.


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## anuragwap

Photonfanatic has some Q2H cyan left, no bin1 cyan or bin6 blue. And those 496nm peak Avago ASMT-JC11-NST01 LEDs should be about 499nm dominant, i.e. still no good


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## Canuke

BVH said:


> Are these your "To Die For" Cyans? I bought a bunch from you waaayyyyy back when and still have them in my parts bins. I had one put in a Fenix pocket light and I have 4 in Mac's 4-Cyan, green cut down mag beauty! Eight power levels up to 1 Amp. Beautiful Cyan color!
> 
> http://www.candlepowerforums.com/vb/showthread.php?146752-Quad-Cyan-*SOLD*&highlight=quad+cyan



I have 5 of these, from Photonfanatic also. I've never seen this color anywhere but a 488nm laser, so I'm pretty sure that's where the peak is, within +/-2nm. I intended them for a clear PC case, with the intention of texturing the clear panels and lighting up the inside "ice blue" with these. I never did build it, as clear cases went out of style around then and I never solved how to get the texturing I wanted. 

I did install one of the "bin 6's inside a cheap host, its color is almost perfectly matched to the Lux V "eye cryin' cyan" Brinkmann I have.


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## SemiMan

anuragwap said:


> I resurrected this old thread since I've found a cheap source of true cyan emitters. Well,not quite. But they are in 495-500nm (bin2 cyan) range. These are the so called 'Exotic LEDs' available through LEDGroupBuy.com. Please do not misunderstand me, I am NOT advertising for them, I assume these are cheap Chinese LEDs with low junction temperature, poor lumen maintenance and are ESD prone, inefficient. But if you want bin2 cyan in high power, its the only sensible way to go. I had emailed the shop owner to test the LED color before ordering. Comparing side by side to my (dull) bin3 cyan Lux-V, I am now sure that these are indeed 495-500nm dominant at 700mA.
> 
> http://www.flickr.com/photos/[email protected]/7754713982
> 
> 
> The other reliable option is ordering 1000+ cyan rebels from Luxeonstar, which is silly. Nichia/Avago has refused to accept bin specific order for high powered cyan LEDs even if ordered in full reel.
> 
> Another option, not very well known is using very low efficiency 1W emitters (490nm peak) from Epitex, a Japanese LED chip manufacturer. These are available from Roithner Lasertechnik/Marubeni America at ridiculously high prices/MOQ.
> 
> There's a Hong-Kong based company called YesLed which seems to manufacture (maybe in the past, probably didn't update their catalog) 485-495nm led dice, but no emitters.
> 
> I made a shower-head arrangement of 5mm LEDs with 217 rank C (495-500nm) NSPE510DS LEDs, resulting severe back pain after soldering the leads! I overdrive the cluster to 2.5-3A(for short time) to get a decent cyan.
> 
> http://www.flickr.com/photos/[email protected]/7754792738



Have you contacted Lumileds/Future Electronics? If you are buying a whole reel, they are likely able to find you a specific reel. If you want a bunch of reels, that may be an issue. There may be some premium of course. It used to be hard to get specific bins as all the good cyan bins went into traffic lights. I am not sure if that is still the case.


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## PhotonFanatic

BVH said:


> Are these your "To Die For" Cyans? I bought a bunch from you waaayyyyy back when and still have them in my parts bins. I had one put in a Fenix pocket light and I have 4 in Mac's 4-Cyan, green cut down mag beauty! Eight power levels up to 1 Amp. Beautiful Cyan color!
> 
> http://www.candlepowerforums.com/vb/showthread.php?146752-Quad-Cyan-*SOLD*&highlight=quad+cyan



Yes, the To Die For Cyan emitters.


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## bshanahan14rulz

What is the Cyan you all are basing your ideal wavelength on? The big beefy argon lasers that peak at 488nm? Lithium or barium borate doubled solid state lasers at 473nm? Just curious, really.


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## anuragwap

Bin6 blue (around 488nm) is true cyan for me for most of the time, but _bin1 cyan_ is perfect when my eyes are adapted to 2700k ambient light.

EDIT: After experimenting hundreds of times with different adapted states, I should say true cyan fluctuates between 485-495nm dominant.


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## PerryScanlon

HarryN said:


> IMHO, there are some big holes in the standard LED color offerings at around 490nm and between "green" and "amber". (sort of like yellow)


Funny! I noticed the same thing, and a lot of "yellow" LED's are in fact amber. Mixing amber and green in the right amount does make a nice lemon yellow, better than a red-green combo.


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## MikeAusC

If you're specifying the colour of LEDs away from 555nm, you need to understand the difference between specifying Peak Radiant Power Wavelength (as measured by an instrument) and Dominant Wavelength as perceived by the eye - the Power Curve modified by the Sensitivity Curve of the eye.

At red and blue there can be quite a difference, though not all LEDs have both figures available in the specifications.


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## EricB

PerryScanlon said:


> Funny! I noticed the same thing, and a lot of "yellow" LED's are in fact amber. Mixing amber and green in the right amount does make a nice lemon yellow, better than a red-green combo.


 I always wondered why they didn't have anything between 570 and 590. Like what would 580 look like? The only pure yellow LED I've ever seen is a phosphor yellow Brookstone keychain light. And that was years ago. I often wonder why that never caught on on anything else.


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## Anders Hoveland

Cree makes a 465-480nm LED, available as a 30 watt chip. And 505nm LED's are also common.
Could these two frequencies be used to fill in the cyan-indigo gap that exists in white phosphor LED's, to give a fuller spectrum?
These might complement the Phillips L-prize quite nicely.


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## bshanahan14rulz

Never fear. InGaN is being pushed to higher and higher wavelengths. It's only a matter of time. Hell, some sample quantities of +500nm GaN resonators have already trickled down into hobbyists hands


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## anuragwap

I contacted Future twice asking for full reel of bin1 cyan/bin6 blue emitters, but they never responded. However, I think I've found the last ray of hope here. The picture shows bin code J1CE, indicating its probably a bin1 cyan, also J means the lower flux bin 60+lumen, supporting saabluster's theory on the first post. These will be unsuitable(too blue) for the traffic signals, maybe that's why they are mounted on starboards. The MOQ was 48 but I still placed an order.


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## anuragwap

FINALLY!!! Thanks a ton saabluster, it was your idea after all to go for the low flux bins. Got 48 bin1 cyan rebels (bin code J1C, i.e. 60-70 lumen, 490-495nm dominant, 2.79-3.03V, all measured at 350mA). I believe the slightly lower flux would not be noticeable in real life.


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## saabluster

anuragwap said:


> FINALLY!!! Thanks a ton saabluster, it was your idea after all to go for the low flux bins.



:thumbsup: Your welcome. Glad that worked out for you.


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## PeDDeR27

Hey anuragwap, do you have any more bin 1 cyans you are selling? I have been looking all over for these!


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## anuragwap

Thanks to a color changing rainbow project, all of my J1C cyans are used up now! So buy in multiples of 48 from here. For bin2 cyan rebels, contact LEDSupply/StevesLED/TCSS etc. (They're not that rare after all)


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## anuragwap

*A new source*

A new source for bin1 cyan leds has popped up: look here (and here for the 3S3P multichip version, but it has worse efficiency). 

The good: Low cost alternative to the J1CE rebels. Color is indistinguishable to J1CE rebels at 700mA.
The bad: The Epiled chips are less efficient than the Lumileds ones (3.7V drop at 700mA). No polarity indication on the bare LEDs. 

I ordered 7 of these but discovered 1 LED was missing just after opening the package. The seller was great, he refunded me $2.50 promptly.










*Update Aug 2014*: In about one and a half year, the silicone domes of these LEDs have started yellowing And they weren't even powered for more than 2 minutes in total. They were kept in anti-static foam boxes from mouser. Another drawback of cheap LEDs!


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## VegasF6

*Re: A new source*

Here is another source I found. I wrote to them and asked for the maker so i could look at a datasheet but they didn't reply. I will probably be ordering some though I don't have any 488nm to compare with. 
http://www.aquastyleonline.com/products/Cyan-LED-3W.html


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## anuragwap

*Re: A new source*

I already talked to them as the spectrum looked quite interesting, here's what they replied:

_Hi,

thanks inquiry!!

the cyan led is more on green side.
but sorry we have not the datasheet on it because it is a customized product.

we can send you a sample to play with, you can just pay the shipping $6 (POST SERVICE 10-12days delivery)

best regards
***_


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## VegasF6

*Re: A new source*

So more like traffic light green I would imagine. Did they tell you who makes the leds?


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## anuragwap

*Re: A new source*

No, they didn't. The spectrum indicates (if its true at all) its a phosphor converted green (i.e. like the Osram's OSTAR for projectors)
My search for true cyan (485-490nm dominant) emitters is still on, till then I'll overdrive J1CE rebels on sinkpad with low duty PWM.

Update (July 2014): 490-495nm cyan Chinese LEDs in XP-E footprint are available on ebay now, for very little price. I've tested some more of them, one was not even properly reflowed.




(I was betting these to be 485-490nm dominant, which sadly they aren't. I'll might try my luck at Aliexpress.)

UPDATE(Nov 2014): Aliexpress sellers are selling blue LEDs covered with green phosphor, as 1-3W 'ice blue' 480-490nm LEDs. They are not true cyan, a pale skyblue with much lower saturation due to the wideband green emission from the phosphor.


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## EricB

*Re: A new source*

Since the discussion of amber and yellow came up, I figured this would be a good place to mention a trick I've discovered to make 590nm (LED or LPS) look like a pure yellow.

Stare at red light, especially at the lightest part (which looks yellowish because it stimulates the green eye cones as well). Eventually, the whole thing looks more and more orange, and long enough, it will itself look almost amber.

Now, look at amber; it looks like a nice lemon yellow (slightly greenish, instead of reddish). Similar to phosphor yellow, but more saturated, like the monochrome amber. At a distance, it's very odd, because it looks not much different from white, yet, again, it's fully saturated. As it gets closer, it looks like a funny "pine oil" golden color, then when it's close, like lemon yellow. 

If you look at blue-green, like 505-515 traffic signal LED's, it looks almost like cyan.

(The colors begin slowly normalizing themselves).


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## JoakimFlorence

*Re: A new source*

At exactly 490 nanometers, the color is right on the edge between blue and green. For any other color LED the wavelength could be plus or minus 15 nanometers and it wouldn't matter that much, but at 490 nanometers there is a sudden cut off. Anything below 490 is blue (a sky blue tint) and above 490 the color has is a very greenish-cyan tint. For this reason, I feel that "true cyan" is a very elusive color. To make matters more complicated, LEDs give off a more trailing amount of longer wavelengths from their peak wavelength than they do of shorter wavelengths. It is commonly said that color LEDs only give off a single wavelength, but this is not entirely true. The wavelength emission from an LED is very narrow, but it is not truly a single wavelength value. So even if an LED had a _peak_ wavelength emission of 490 nanometers, chances are the color is going to be more green-tinted than 490 nanometers. 

If you want to get an idea of what 490 nanometers actually looks like, look at the faint blue-green terbium spectral line from a fluorescent lamp. Either use a prism or a diffraction grating and hold it up to the light. You can also use an ordinary CD, just stare into the reflection at the right angle. You will notice that even the spectral phosphor line is not entirely a single discrete wavelength (though it is very narrow). On one edge of the line a faint light blue turquoise will seem to predominate, while on the other side it looks more greenish cyan. This spectral line is right on the border between blue and green. 

If you ever get the opportunity, look at the 488 nanometer line from an argon laser. It is a sky blue color, with just a little cyan hint, but definitely and distinctively blue. 

You can find cyan bin LEDs being sold on ebay, marked as 490 nm, but many people who buy them will be disappointed. They're not truly a _real_ cyan color, not quite. Although I suppose the definition of "real cyan" can be a little subjective. I mean they're definitely not on the bluish-side of cyan. I suspect these LEDs may actually be putting out an emission closer in the territory of 490-495 nm.

To make matters more confusing, 505 nanometer "traffic signal" LEDs are commonly called "cyan" although they certainly aren't. They are, however, more cyan than 520 nm, which is a forest green color. I suppose it's all relative, to some degree.


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## JoakimFlorence

*Re: A new source*



EricB said:


> If you look at blue-green, like 505-515 traffic signal LED's, it looks almost like cyan.
> 
> (The colors begin slowly normalizing themselves).


I agree. Saturation effects can make it very challenging to accurately judge precise color tint. Those 490 nm LEDs look kind of bluish for the first instant you look at the light, but after a while the eye starts adjusting and they begin to look more and more greenish than anything else. And all the surroundings look rose-tinted when you look away. 

It is incredibly difficult to discern where precisely green ends and blue truly begins. It depends on how you look at it (literally) and I suspect relative color contrast plays a large part in our perception. When I look at green for a few seconds and then look at the blue-green spectral line it looks kind of blue. But then when I look at blue light for a few seconds and then look back at the spectral line it looks like a turquoise green. Obviously the spectral line does not change but my precise perception of the color hue changes. It is nearly impossible to decide objectively whether the line is more green or more blue. 

For this reason I would consider it truly cyan, since I cannot objectively differentiate whether it has a little bit more green in it or a little more blue. It just seems blue-green, and that's all that can be said about it.

I'd really be interested if they made a bluish cyan colored wavelength LED, but alas, those are impossible to find. Kind of like the same color as those old VFD tubes that were used in the 1980s.


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## JoakimFlorence

*Re: A new source*

I just noticed that the LED digital display on my kitchen microwave is true cyan. 

Not very high light output though.


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## BVH

*Re: A new source*

I still have this beauty by Mac and it is my all-time favorite light. Hardly use it but it's always in view when I'm on the PC. It uses the Q2H bin LED. Looks very Cyan to me when in the higher current modes. I also had the same bin LED put in an old Fenix L1P

http://www.candlepowerforums.com/vb/showthread.php?146752-Quad-Cyan-*SOLD*


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## archimedes

I have a nice cyan light engine, that was included in a large group of assorted vintage McLux parts I got a while back, and now runs in a Mirage_Man host ....

Sorry I don't know the details on the emitter, however


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## JoakimFlorence

Just got stopped by a police car. But what I noticed was the blue and red lights. The blue LEDs appeared to be a very soft slightly cyan-tinted blue hue, it definitely could be 485-490nm. 

I know what 470nm and 480-485nm looks like, and these were not that color. But I just have difficulty believing the police lights could actually be using 485-490nm because I have searched everywhere and never seen that wavelength range available (at least not in >1W LEDs), so I'm considering if there could be some other explanation. Maybe the LEDs could be "ice blue" emitters and they only appear like 485-490nm behind the blue color filter. Ice blue emitters can commonly be purchased in cheap automotive lighting products and consist of a 470nm emitter covered by a little bit of green phosphor. These normally appear like a whitish blue, but passing through the blue plastic, that could be altering their spectrum. However, most ice blue emitters I have seen appear to be a more bluish color hue than cyan, so I'm not sure how plausible that is. These would probably have had to have been much more greenish ice blue emitters (edit: I think these are called "aqua blue"). Theoretically, passing such a "cold green" light spectrum through a blue filter could lead to a spectrum that contains 470-500nm wavelengths, and this could superficially appear similar to 485-490nm. Maybe.

Apparently there are some Japanese companies manufacturing semi-high power LEDs in this wavelength region.

Epitex L490-06 5mm greenish blue, peak wavelength 490nm typ.

Murubeni SMC490 SMD LED greenish blue 490nm typ. 
20mA 3.5V brightness 75mcd

The specifications show that these LEDs appear to have very wide spectral emissions about 30nm half width 
480-500nm minimum and maximum

Unlike those "490nm cyan" emitters found on ebay, these 490nm Japanese emitters are clearly categorized as "blue".


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## CuriousOne

I've measured some "cyan" emitters from ebay, with spectrophotometer. They have quite wide emission range, so using specific filters, it is possible to get "real" cyan from them, but at very high brightness cost.


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## CuriousOne

Bought some "480nm Cyan" leds from ebay. They are actually a blue leds with 450nm peak, wtih 520nm phosphor applied


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## JoakimFlorence

CuriousOne said:


> Bought some "480nm Cyan" leds from ebay. They are actually a blue leds with 450nm peak, wtih 520nm phosphor applied


Yes I know. This is very common if you cheap LEDs from China.


Update on the police car lights: I happened to see a police car driving by and the exterior blue-color filter plastic was cracked and I could distinctly see an LED emitter lit up inside. It seemed like it was kind of dangling a little bit on a strip, so apparently there had been some damage. What was interesting was the color of light being given off by this emitter, it was a whitish green-turquoise. I could not make out the color exactly since it was daytime but it had to be either a 495nm emitter or a green phosphor-converted emitter. Very interesting. What was _this_ LED doing behind a blue color police light?

My conclusion: there are three possibilities. The first is that they are using 495nm cyan-green mixed with 470nm to achieve the optimal blue tint. I don't find this particularly likely since it's very rare for commercial products to mix different wavelength LEDs just to achieve something this subtle. The next possibility is they are using 495nm behind a blue filter. The blue filter would shift the color tint to blue (or a bluish cyan). Could be possible, but very inefficient, would cut down at least 60% of the light output, but that's cheap chinese engineering for you. The last possibility is phosphor conversion, and I actually have some of these chinese emitters. They are very cheap, and the color is whitish-green, or sometimes bluish-green (depending on the bin color). The bluish part comes from blue light from the emitter shining through the phosphor. I find this last possibility most likely. I didn't get a good look at the emitter but it appeared to be SMD-type. These green phosphor LEDs contain a trough in the cyan part of the spectrum that's about 60% lower than the green or blue maximum. So the spectrum is all filled in but there's just a deficiency of wavelengths in between maybe around 510 to 475nm. You put a blue color filter in place and that could potentially make the wavelength graph about level. This isn't all that different from using 470nm blue because the underlying emitter in these greenish phosphor LEDs (the cheap chinese ones I'm familiar with) is 470nm (not the usual 450-455nm in white LEDs). From the type of color of light I saw (coming from the bare LED), these would give off some 470nm blue light but there wouldn't really be a blue spike in the spectrum because the blue is much lower than the green. So here you have a simple, albeit inefficient, way of achieving a mostly smooth spectral distribution with the right color tint. And I'm sure these lights are manufactured in China.


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## CuriousOne

I have a segment of blue led cluster, removed from police car (These small sections of blue and red that go besides front vent openings). It has 5mm blue leds and additional blue filter in front. Will measure spectrum tomorrow.


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## CuriousOne

Oh, forgot to say, I found a seller of 5mm "true" cyan 582nm leds on taobao, who claims that 482nm claim is 100% true. I've ordered some, and they are on the way, let's see how it will go.


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## CuriousOne

These LEDs arrived, and as measurements show, he was correct, these are true cyan, single die, no phosphor or double crystals, just pure cyan leds.


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## anuragwap

Cheap 3535/XPE styled 'epileds' 490-495nm cyans when mounted on *DTP copper boards*, driven at 1 amp and properly heatsinked, blue-shift noticeably more my bin1 luxeon rebels mounted on sinkpad mounted on oversized ohmite heatsink. I don't have a spectrometer, but I guess the color is very close to 488nm dominant. 




CuriousOne said:


> These LEDs arrived, and as measurements show, he was correct, these are true cyan, single die, no phosphor or double crystals, just pure cyan leds.


Although 482nm might be too blue, still will be an uncommon color. Can you please share the source with the rest of us?


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## BVH

I just acquired a Sekonic C-7000 Spectrometer and measured the PhotonFanatic "To Die For" Cyan emitters in my Mac's Quad Cyan light. The Peak Wavelength is about 495-497 NM. When the light is on HIGH, it appears very Cyan to me with a small bit of green. Lower levels produce more green. Has anyone decided what NM wavelength is really Pure Cyan? Is the 490-495 the best that can be had these days? If so, a source would be appreciated.


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## FRITZHID

488nm? Seems to be the most cyan-y cyan to my eyes.


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## anuragwap

BVH said:


> If so, a source would be appreciated.


If you want to go the luxeon rebel way, see TCSS (at the bottom, they say all their cyans are bin1), but do contact them beforehand to make sure if they are indeed bin1. If you hate their steep price (I do), order some cut tapes of 'lxml-pe01-0060' from mouser/digikey/future and there is a very good chance of them being bin1 cyan. (You have to reflow them onto starboards though)

If you can live with the low lumens and high V_f of epiled chips, get them from aliexpress or ebay by searching '490nm cyan led' and order the ones that look like cree xp-e. As noted, you need to desolder and reflow them onto dtp copper boards to unleash their full potential. Realizing this, some chinese sellers on Ali are also offering them on flashlight friendly 16mm / 20mm dtp stars.


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## JoakimFlorence

BVH said:


> Has anyone decided what NM wavelength is really Pure Cyan?


In terms of a spectral line (like something from a laser) I believe exactly 490 is cyan, where most people would be unable to differentiate whether the color looks more greenish or more bluish. 
However, this does NOT translate over to a 490nm LED (so don't make that assumption!). There are two reasons for that. First, virtually all of the Chinese sourced "490nm" emitters that you will find anywhere should more accurately be described as 490-495nm and probably peak somewhere at about 492nm (this is just what I believe, from my personal observations). The second reason is that LEDs do not actually truly give light out at a single discrete wavelength value (although it is relatively narrow). The bandwidth of emissions trails off further towards the longer wavelengths. Normally this does not lead to any color difference, but when we're talking about LEDs in the cyan territory it's a different story, since the transition from blue to green is very sudden. This means that, in practice, a cyan LED is going to appear somewhat more greenish than its peak wavelength value would be. A real 490nm LED would probably not appear exactly the same color hue as a 490nm laser.

488nm is a very beautiful light blue color with a tinge of cyan.​
I have shopped around quite a bit and all of the LEDs advertised as 490nm were, what I would consider, a bit more on the greenish side of cyan. One of them was even covered with a thin bluish colored piece of plastic film that appeared to be designed to try to shift the color a little bit more towards a truer cyan (although it was only half-way successful towards this end, in my opinion).

So, to conclude this post and provide a simple answer to your question, if you wanted a true cyan color it would have to be a 489 nanometer LED (or to be more broad, a 488-490nm distribution, although I'm sure a 485-490 would be quite a lovely blue-cyan as well).


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## ssanasisredna

You are going to always be fighting both the spectral content of the "cyan" LED which is usually quite wide, and the eyes drastic shift in efficiencies in that area.

Perhaps the best way to do this is with a filter? http://www.saikoled.com/scientific.html <-- They do it with very expensive filters, but there could be a lower cost solution out there? It all depends on how perfect you want your cyan. If it's for a flashlight, then maybe some of the Polymer optics mixing optics designed for Luxeon rebels and adding together blue and green to a cyan to get your best perception of cyan. It will be like looking at cyan, but not like illuminating with cyan.


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## anuragwap

Off topic, but just noticed that DTRLPF now has 55mW 490nm Sharp diode lasers in his website for $50, they do 160mW when pushed.


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## WeLight

We stock the Nichia Cyan which we sell to aircraft landing light company so they are as cyan as we have seen


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