# Yuji BX series Hi Cri 5mm LED



## Vortus (May 6, 2015)

Has anyone used these? Modifying my wife's old Black Diamond Zenix IQ. It has a center main led and a 5 mm on either side. The center was already moddedonce before to a p4. The 5mm are angry blueish purplish white and are still stock. Changing the center again to an XRE w an optic for some throw. So the 5mm will need to go to reading duty. If the color is good anyway. Found these Yuji BX series and wondered if any had tried them. Or any suggestions. The forum search results were a bit dated so hoping new ones are out there. 

Yuji BX series Hi Cri 5mm LED
>93 Cri
3200k or 5600k
30 degree or 60 degree


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## Anders Hoveland (May 7, 2015)

I agree 93 CRI is a good compromise between color rendering and efficiency, but I still think the efficiency would been substantially higher if it had been a more reputable company (like Cree) who had decided to make this 93 CRI emitter.


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## idleprocess (May 7, 2015)

3200K is an unusual option - tempted to order some and see how they work.


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## Anders Hoveland (May 7, 2015)

idleprocess said:


> 3200K is an unusual option - tempted to order some and see how they work.


3200K is a great color temperature, in my opinion. It's a bright white, but still warm, and not as 'unnatural' as 3500K. 
It's the type of vibrant light you would want in your kitchen, or a casual church meeting room. 3200K spotlighting is also sometimes used as exhibition lighting for modern art.
Not really "relaxing", but still within the range of being residential.


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## lyyyghtey (May 29, 2015)

Yes I have used these very LEDs, in 3 of their 4 variations. Only 3200 30deg not tried. They are excellent, far beyond the color appearance of any other 5mm LED I have ever seen, even the Nichia GS, which tends to have an inconsistent color across the beam and still isn't as high CRI.

I went a Googling for high CRI 5mm LEDs almost a year ago originally to make proper Christmas light strings I could actually use to light my house. I've since done that, and many more smaller projects with them.

The Vf tends to be in the range of 2.8 to 2.95 @ 20 mA which is pretty good! Also they are at least as, and often more, efficient than most other 5mm white LEDs I've played with, in spite of being high CRI.

The white light (there is no tinted center or fringes for all practical purposes) is very even with only very minute artifacts in the beam profile which are not noticeable unless white wall hunting and which go away if you use several. 

The 30 deg ones spit considerably more light out the rear of the package than the 60s, but still a small percentage of the total.

The leads are unusually short. They're prefect for relamping most LED Christmas lights without cutting the leads! Cathode 14.5mm, anode 17mm.

I've used 10 (8 @ 60deg and 2 @ 30) to mod the typical 3AAA headlamp you always see and it made the lamp go from unusable-ugly and unusable-narrow to awesome! Won't ever be as bright as a power LED headlight but fine for anything not requiring this power. The beam spread is between a Zebra pure flood and a floody beam, which I wish were available more. 

The shipping is significant so you'll probably want to anticipate future needs as best you can and put together a larger order.

Do not hesitate to order these in whichever color temp you prefer if you have any need for 5mm white LEDs! Just like the Nichia 219 high-CRIs, the 5600K might at times appear to have a slightly pinkish tint. I theorize this may be due partly to the fact we're so used to LOW CRI artificial sources with their poor red content and often unnecessarily greenish tint (fluorescents including most daylight CFLs come to mind)  Odd that triphosphor fluorescents can have a CRI of 82 to 85 and yet look so bad! (due to the greenish tint and lack of deep red, mostly) They get greener when the tube overheats, which isn't hard to accomplish. Also I believe some manufacturers intentionally tint them green to get higher lumen ratings ... The original TCP daylight CFLs (6500 and 5100 K) did not have this green problem, though still lacked deep red of course. But I digress.

Check out Yuji's other offerings too. I ordered some VX series COB LEDs to try out but haven't had time to build into anything yet! :scowl: bench tests were amazing though!


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## lyyyghtey (May 30, 2015)

lyyyghtey said:


> Do not hesitate to order these in whichever color temp you prefer if you have any need for 5mm white LEDs! Just like the (original 219A) Nichia 219 high-CRIs, the 5600K might at times appear to have a slightly pinkish tint. I theorize this may be due partly to the fact we're so used to LOW CRI artificial sources with their poor red content and often unnecessarily greenish tint (fluorescents including most daylight CFLs come to mind)



Yes, though I might have an additional explanation for this pinkishness. I just received some LXW9-PW27 emitters yesterday. Great part, seriously underappreciated! I ordered them because their spectral power distribution shows their red peaking around 645-650nm, whereas most hi-CRI warms peak around 630. I didn't like the way the CREE hi-CRI warm makes deep red fabric look more orangeish. After reflowing a couple I played with them, a CREE warm hi-CRI L10, and an incan Poly Stinger. Well Lumileds has fixed that orangeish-reds problem! And a new one popped up: the light looks... pinkish. 

It appears that with blue pump phosphor converted hi-CRI, you may be able to have either a normal-incan-yellowness beam (talking white wall hunting here) OR a correct, black body-ish rendering of deep reds, but maybe not both at the same time. I suspect this is due to a combination of where in the red spectrum the LED gets it's warmness from, and the dip between the blue peak and the green/yellow phosphor response. If it gets its warmth more from the deeper reds so as to render deep red properly, then the yellow-oranges will be shirked somewhat. That combined with the blue spike and subsequent aqua/deep green dip creates pink. (Or lavender in higher CCT emitters with a taller blue spike.) 

Getting back to Yuji's products, I'm guessing the violet pump will pretty much solve this pink beam tint versus orangeish deep reds tradeoff, since the spectrum is continuous and mostly black-body-shape-ish from blue to red. Yet to be seen. Onward and upward!


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## SemiMan (May 30, 2015)

How long did you allow your eyes to adapt to the LED light source and I assume that you were exclusively using said light source and no other light source when arriving at the orangy/pinky conclusions?


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## lyyyghtey (May 30, 2015)

SemiMan said:


> How long did you allow your eyes to adapt to the LED light source and I assume that you were exclusively using said light source and no other light source when arriving at the orangy/pinky conclusions?



It didn't take very long. I powered it up to 350 mA to get my rough Vf reading and noticed it almost immediately. It reminded me of the color of a Sylvania MR16 I have that uses high-CRI Oslon Square LEDs so that made me start A/B comparing the Rebel with the CREE and incan. (I don't have any of the Oslon separated out yet). In doing all comparisons I do my best to make both sources look the same brightness at the surface I'm illuminating.

I assume with this as any other source I use, if I used it for any length of time with nothing to compare it to, it would soon look normal. I haven't put it in a light yet but soon will!

The deep red fabric I used was Christmas ribbon I sought out using a Nichia 219 light. I looked for ribbon that appeared a dingy maroon under the store's triphosphor fluorescents but sang with rich red when hit with the Nichia! I've also identified a deep red collared shirt at Wal Mart this way and a type of red velvet sold by fabric stores and commonly used on Santa costumes. Theres also a type of fringe material sold at some craft stores. I have yet to find a single example of deep red knitting yarn There is a deep red paracord (correctly named even!) but it's brightness value is lower than the materials above. I've found that there aren't too many materials that respond visually more strongly to deep red than to orange-red (615nm or so) out there. When they do occur they're fairly easy to find because of the eye being less sensitive to deep red: it really has to be a strong difference to be noticeable.


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## SemiMan (May 31, 2015)

lyyyghtey said:


> It didn't take very long.
> 
> I assume with this as any other source I use, if I used it for any length of time with nothing to compare it to, it would soon look normal.




This is the thing. If you are presently using one type of light, then turn another type on, you cannot make any valid comments on that second light, other than by comparative .... and even then that is debatable.

You really need to let your eyes adapt completely and then determine if the light quality is good.


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## lyyyghtey (May 31, 2015)

SemiMan said:


> This is the thing. If you are presently using one type of light, then turn another type on, you cannot make any valid comments on that second light, other than by comparative .... and even then that is debatable.
> 
> You really need to let your eyes adapt completely and then determine if the light quality is good.




Your first point is true, if the sources being compared are all someone's (some company's) interpretation of what such light should look like. However my comparisons were between one LED, then the incandescent, then the other LED, then the incandescent. All this I do rather rapidly so as to purposely make differences obvious which would otherwise be hard to detect due to adaptation. (With deep red comparisons, adaptation is hurtful because reds turn orangey if I stare at them for awhile, saturation wise.) As to your second point, I was comparing specific, narrowly focused features, not overall goodness or quality. It's a very theoretical sort of thing I like to do that helps me "understand" a source. I'm not knocking any particular source or CCT or color. I use 'em all for something or other, even an occasional greenish XM-L2! (Oslon EQ white! Rebel lime!!!) Just pointing out differences I see.

In all of this I am making the assumption that incan is as close to standard as I'm going to get in terms of color rendition, measured in CRI or otherwise, at that warm color temperature inrange. Incan is my standard, though not perfect for every warm white application, because I don't have access to any other standard that everyone else knows by which to describe differences I perceive.

In many cases I would want a pinker source than incan, for romantic appeal or whatever, to the point of adding filters to an already pinkish LED (perhaps for an eating area). When trying to blend in with existing incans where the sources are visible, or where yellow/green colors need to be prominent (lots of plants to look at perhaps), I would prefer a yellower overall tint. Though granted, not often yellower than incan.

With all these LEDs being 90+ CRI, any of them used by itself would satisfy my needs well. In fact I seriously doubt I'd mind using them side by side in many instances. They really all seem to be very good! I'm just finding it interesting and theorizing why I have yet to find a blue-pump warm source that mimics incan in terms of both yellowness on a white surface, and appearance of a deep red surface, at the same time. You could say I am overly focused on deep red given the rarity of true deep red materials and I concede that it's just a personal preference at that level. But deep red does affect somewhat how other reds appear since most red material i've ever tried responds over seemingly the whole range of red.

Both of those comparisons, though together a seriously incomplete picture of color accuracy, are items I find important for a source to mimic an incan. I tend to look for them almost automatically, which led to using high -CRI for all my living/working spaces. I also look at teal, especially does it appear too blue or green for the given CCT (also as compared to incan), since wavelength discrimination is so fine in that range. I don't expect blue to be totally accurate given the necessary blue spike with this technology. I find it easiest to detect blue errors when looking at the source through blue filters of some sort. Thankfully, for most purposes metamerism and the relative suppression of blues at warmer CCTs seem to make these errors largely unimportant.

Lastly, I'm obviously paying an efficiency price in having more deep red in the source. That would need to be a fair trade for the application in question.

Sorry for the length this reply became! I hope it makes some sense why I'm doing these eccentric comparisons!


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## KITROBASKIN (May 31, 2015)

Sounds interesting to me. Hope you don't lose the forest for the trees...


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## Anders Hoveland (Jun 1, 2015)

lyyyghtey said:


> Yes, though I might have an additional explanation for this pinkishness. I just received some LXW9-PW27 emitters yesterday. Great part, seriously underappreciated! I ordered them because their spectral power distribution shows their red peaking around 645-650nm, whereas most hi-CRI warms peak around 630. I didn't like the way the CREE hi-CRI warm makes deep red fabric look more orangeish. After reflowing a couple I played with them, a CREE warm hi-CRI L10, and an incan Poly Stinger. Well Lumileds has fixed that orangeish-reds problem! And a new one popped up: the light looks... pinkish.
> 
> It appears that with blue pump phosphor converted hi-CRI, you may be able to have either a normal-incan-yellowness beam (talking white wall hunting here) OR a correct, black body-ish rendering of deep reds, but maybe not both at the same time. I suspect this is due to a combination of where in the red spectrum the LED gets it's warmness from, and the dip between the blue peak and the green/yellow phosphor response. If it gets its warmth more from the deeper reds so as to render deep red properly, then the yellow-oranges will be shirked somewhat. That combined with the blue spike and subsequent aqua/deep green dip creates pink. (Or lavender in higher CCT emitters with a taller blue spike.)


Within the last few years they have recently developed bluish-green aluminate phosphors that can efficiently fluoresce from a 450nm blue emitter. These phosphors have fairly broad spectral coverage, emitting 40% of peak even down to 480nm. 



lyyyghtey said:


> Getting back to Yuji's products, I'm guessing the violet pump will pretty much solve this pink beam tint versus orangeish deep reds tradeoff, since the spectrum is continuous and mostly black-body-shape-ish from blue to red. Yet to be seen. Onward and upward!


Yes, this is indeed true. I have a Yuji violet-pumped LED. The overall color of the light actually appears a just a little greenish-tinted– at least compared to any other LED I have seen– but not really in an all bad way. The color rendering is completely perfect, fully saturated reds and emerald greens, deep indigos and azure cyans. The color temperature is rated 5000K but the really weird thing about it is the light almost feels much more like halogen than any 3000K regular LED I have seen—basically it feels like what halogen light would look like if it came in a higher color temperature.

I think in a regular blue-pumped LED if you have more deep red in the spectrum, there also has to be more cyan to balance out the color tint. But there can only be so much cyan in an LED. I was playing around with Osram's LED spectrum software and came to the conclusion that a blue-pumped LED cannot have too much bluish-cyan in the spectrum otherwise it will throw off the blue color rendering, blue-emitter LEDs do not have a broad spectrum of shorter royal blue wavelengths to balance it out. Like you alluded to, this may explains why most high CRI LEDs (even those that are not particularly trying to be really efficient) peak at 635nm rather than at a deeper red value.


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## Anders Hoveland (Jun 2, 2015)

lyyyghtey said:


> It appears that with blue pump phosphor converted hi-CRI, you may be able to have either a normal-incan-yellowness beam (talking white wall hunting here) OR a correct, black body-ish rendering of deep reds, but maybe not both at the same time.


While I think this is indeed a keen observation, this does not necessarily _have_ to be the case. I have some high CRI Oslon SSL 4000K emitters, and they do not have a pinkish tint, yet they render red colors excellently, as near as my eyes can discern. Of course, these probably aren't your typical high CRI emitters, I might be a little spoiled. I looked at the spectral graph in the datasheet and selected these emitters because I thought it looked like they had more bluish cyan spectral coverage than the other high CRI emitters. Notable here is that they also seemed to have slightly less deep red wavelengths than the other super high CRI emitters. The datasheet claimed an astounding "96CRI typical" for these emitters, and I have no doubt it would have gone up to 97CRI had they chosen to add more deep red wavelengths into the spectrum, though that would have substantially cut into efficiency, and going by your theory, probably have thrown off the tint too. According to the datasheet, the R9 red value is still very good (>90) but not quite as high as some of the other super high CRI emitters (97-98), still the red color rendering looks very good to me, does not look orangish-hued at all. Of course, this might be because the color temperature is 4000K, at higher color temperatures reds often have more contrast (because there is so much green), so the R9 value might be a much more important factor for red contrast in 2700K LEDs.

The red in the spectrum of these emitters peaks at 635nm, by the way. The spectrum still contains plenty of deeper red wavelengths though, so the red phosphor peaking at 635nm is not bad (i.e. it's not as if _all_ the red wavelengths in the spectrum are 635nm). The red phosphor in some of the lower (80-85) CRI LEDs peak at around 610nm, for comparison (judging by the spectral graphs).

In any case, I would be very interested in any product put out by Yuji, but I do not think they have perfected their blue-pumped LEDs quite to the same degree as several other companies have, probably because they assume that anyone who wants extremely high CRI will just go for their violet-pumped emitters, that's the main product this small Chinese company is known for.


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## Anders Hoveland (Jun 2, 2015)

I was grabbing all sorts of different red objects sitting around my home, trying to compare the R9 deep red color rendering between halogen and a 95CRI LED spot lamp (and the light does not have a pink tint, by the way). I could not discern any difference. Maybe reds look just a tiny bit more saturated under halogen, but any difference was a notch below what I could reliably discern, and I am adept at noticing subtle differences. Perhaps the difference is more noticeable using a 93CRI emitter?




lyyyghtey said:


> I've found that there aren't too many materials that respond visually more strongly to deep red than to orange-red (615nm or so) out there.


I believe this is true. I was researching spectral reflectance graphs for various natural red colors: red apples, red roses, pink human skin. Red plant pigments reflect only slightly (25%) less red-orange 615nm than they do red 650nm, while with human skin the ratio is about equal (but human skin also reflects a little greenish yellow as well, which is half the reason skin tends to be more orange-toned).


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## lyyyghtey (Jun 5, 2015)

KITROBASKIN said:


> Sounds interesting to me. Hope you don't lose the forest for the trees...



That is always a danger! After awhile I have to just go back to using one particular light and enjoying it! I tend to have a range of lights I use regularly and I suppose this helps prevent my becoming used to one particular torch as being my 'normal'.


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## lyyyghtey (Jun 5, 2015)

Anders Hoveland said:


> Within the last few years they have recently developed bluish-green aluminate phosphors that can efficiently fluoresce from a 450nm blue emitter. These phosphors have fairly broad spectral coverage, emitting 40% of peak even down to 480nm.



Interesting! That probably helps explain the surge in hcri sources lately and the improvement in cyan performance I've been noticing! I presume these are a supplement for use in HCRI sources in the same way red phosphors supplement the standard ones? I wonder if this is what they're using in the Oslon EQ white? I don't have any of those yet, but intend to get some soon. I do have a blue-green-yellow PC Chinese LED that may be similar- I should analyze it's spectrum more carefully! I also have Rebel lime, and they're awesome! 

Sounds like I really need to try an Oslon SSL 4000K source! I have the 3000K MR16 made with hcri Oslon Square and like it a lot, and that might not be as good as the new SSL 150s they have.




Anders Hoveland said:


> Yes, this is indeed true. I have a Yuji violet-pumped LED. overall color of the light actually appears a just a little greenish-tinted– at least compared to any other LED I have seen– but not really in an all bad way. The color rendering is completely perfect, fully saturated reds and emerald greens, deep indigos and azure cyans. The color temperature is rated 5000K but the really weird thing about it is the light almost feels much more like halogen than any 3000K regular LED I have seen—basically it feels like what halogen light would look like if it came in a higher color temperature.



I just went back and played with my 5600K Yuji VX COB,, because I have yet to swap it into a desk lamp I made still containing its original XR-E cools! I can confirm what you have said. It reminds me very much of my days before daylight fluorescents, when I would gel 90W halogens to about 5000K for my work desk! It got replaced with linear fluorescent due to heat issues(!) being in the desert, but I lost a lot in color rendering! Granted the incan and gels (cine CTB filters) aren't perfect either but they were a TON better than triphosphor! This Yuji also reminds me of Sylvania silver Star headlamps, though they're 4000K.



Anders Hoveland said:


> I think in a regular blue-pumped LED if you have more deep red in the spectrum, there also has to be more cyan to balance out the color tint. But there can only be so much cyan in an LED. I was playing around with Osram's LED spectrum software and came to the conclusion that a blue-pumped LED cannot have too much bluish-cyan in the spectrum otherwise it will throw off the blue color rendering, blue-emitter LEDs do not have a broad spectrum of shorter royal blue wavelengths to balance it out. Like you alluded to, this may explains why most high CRI LEDs (even those that are not particularly trying to be really efficient) peak at 635nm rather than at a deeper red value.



That sounds about like what I've been noticing. That strong blue spike combines with the deep red as there isn't enough cyan to balance it out and sum the deep red to white. So the red has to be shallower to avoid creating pink and so it will sum to white with the 450-ish nm blue spike along with the yellow-greens. That does seem to make it look like the new phosphors are a partial way out of this problem, compared to the older phosphors that resulted in the SPD graph going almost to 0 between the pump and the converted parts.

I'm thinking of a bad example of this in a (unfortunately lighting) store here. They have WW LEDs at the front counter, but they're the 80 CRI variety, at best. All the blue objects on display look a strong royal blue, even though the overall lighting appearance is warm. It's an odd sensation!

Of course a full solution for the blue spike problem is to have the pump be outside the visible spectrum, into the UV, and don't pass it through the phosphors at all. But I realize there are still severe efficiency issues with this approach and I don't even know if it's possible in any form that could be used commercially.

Edit: I just thought of another possible solution: have a blue pump composed of many smaller blue chips, spread out in spectrum over the 435nm to 460 nm or so range so as to more closely mimic the black body spectra at that point on the Planckian locust. Along with some of the newer phosphors. I know many phosphors have a fairly wide possible pump range, so I wonder how that would affect the phosphor-converted portion of the spectrum?


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## lyyyghtey (Jun 5, 2015)

I've placed one of the beautiful pinkish LXW9-PW27 Rebels in a host and am playing around with it and other lights I have, including hcri LED bulbs from various brick and mortars...most of these lights do not have a pinkish tint. I'll see which of them gives what kind of red rendering as compared to incan. Future post! Work is about to get busy again in a couple days though so I'll see how far I get.


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## Anders Hoveland (Jun 5, 2015)

First I want to say really nice post! 

You asked several questions so I will try to address them all.




lyyyghtey said:


> I wonder if this is what they're using in the Oslon EQ white?


Unfortunately, not. The EQ white emitters are highly efficient, but they are basically just a yellowish-green phosphor that is a little off-white tinted. 
They are very deficient in cyan. 

I started a thread about this:
http://www.candlepowerforums.com/vb...-EQ-white-LED-emitters-now-available-for-sale




lyyyghtey said:


> Sounds like I really need to try an Oslon SSL 4000K source!


The SSL family comes in three different levels of color rendering. Be sure to get the high CRI version. 




lyyyghtey said:


> I just went back and played with my 5600K Yuji VX COB,, because I have yet to swap it into a desk lamp I made still containing its original XR-E cools! I can confirm what you have said. It reminds me very much of my days before daylight fluorescents, when I would gel 90W halogens to about 5000K for my work desk! It got replaced with linear fluorescent due to heat issues(!) being in the desert, but I lost a lot in color rendering! Granted the incan and gels (cine CTB filters) aren't perfect either but they were a TON better than triphosphor! This Yuji also reminds me of Sylvania silver Star headlamps, though they're 4000K.


Yes, the very best quality of light comes from filtered halogen, but unfortunately this is very inefficient in terms of energy, and produces a large amount of heat to generate a small amount of light when you want to go up to 4000K. 

A little extra heat is not a bad thing in cold climates, where in the winter it can start to get cold and dark early in the evenings, but if there is sweltering heat, you have good reason not to want to leave a 200 Watt filtered halogen lamp on.




lyyyghtey said:


> That does seem to make it look like the new phosphors are a partial way out of this problem, compared to the older phosphors that resulted in the SPD graph going almost to 0 between the pump and the converted parts.


Yes, phosphors are a _partial_ way out of the problem. It is still not going to be completely perfect because there will always be a dip between the blue and the peak green emission (unless you put some sort of filter over it I suppose). It is a little too complicated to go into an explanation why that is. 
On the other hand, a little dip in the spectrum is a desirable thing, it helps compensate to some extent for the lack of deeper indigo wavelengths to better be able to render saturated blue hues. 



lyyyghtey said:


> I'm thinking of a bad example of this in a (unfortunately lighting) store here. They have WW LEDs at the front counter, but they're the 80 CRI variety, at best. All the blue objects on display look a strong royal blue, even though the overall lighting appearance is warm. It's an odd sensation!


I agree with you. It's probably something many people do not notice, but it just does not look quite right. I actually think just a very small amount of LED light in a room can accentuate the deeper blue colors, but it does not take more than 20-30%. Once you add too much LED light in the room, all the blue hues start looking the same.




lyyyghtey said:


> Of course a full solution for the blue spike problem is to have the pump be outside the visible spectrum, into the UV, and don't pass it through the phosphors at all. But I realize there are still severe efficiency issues with this approach and I don't even know if it's possible in any form that could be used commercially.


They can be used commercially, but typically only in small spotlights for much higher end applications. Even the high CRI blue-pumped LED spotlights found now in many commercial spaces are usually not used as the _main_ source of lighting. Using a violet emitter to pump the phosphors results in a decrease in efficiency of about 20-30%. Using deep red phosphors for higher CRI LEDs also results in a substantial loss in efficiency, although they are working to develop more efficient red phosphors (Nexxus Lighting has made commercially available an R30 lamp with remote phosphor that uses quantum dots in the formulation for higher efficiency).




lyyyghtey said:


> I just thought of another possible solution: have a blue pump composed of many smaller blue chips, spread out in spectrum over the 435nm to 460 nm or so range


Unfortunately there are no commercially available LEDs that emit over the 485-490nm (greenish-blue/azure) range, which is what you would probably need to truly balance out the shorter deeper blue wavelengths. It is not easy to get around this, if it was you would think that one of those custom D.I.Y. reef lighting hobbyists would have stumbled on a combination that produces light that feels exactly like daylight, which I have yet to hear happening.
If you want to discuss the topic further of combining separate emitters to produce a better spectrum, I suggest we take the discussion to this thread:
problems encountered trying to make a DIY super high CRI array 




lyyyghtey said:


> I know many phosphors have a fairly wide possible pump range, so I wonder how that would affect the phosphor-converted portion of the spectrum?


Not a problem. Phosphors generally do not have a problem being excited by shorter wavelengths. In fact, if you look at a phosphor excitation spectrum graph, the excitation efficiency typically decreases much more rapidly at increasing wavelengths than decreasing.



lyyyghtey said:


> so as to more closely mimic the black body spectra at that point on the Planckian locust.


When it comes to higher color temperatures, I actually do not think mimicking the black body spectrum is what we should be aiming for.
Natural sunlight (after being attenuated through the atmosphere) does not have quite the same spectral distribution as a true blackbody curve, the violet and shorter blue wavelengths tend to get a truncated off to some degree, Rayleigh scattering being mathematically proportional to the _*fourth*_ power of the wavelength in question.

Many people say that they find higher color temperature artificial inside lighting to be too harsh, but I think a 4000K light source might be a lot more popular in people's homes if it more closely tried to approximate the spectrum (and color tint) of _natural_ light rather than a _true_ 4000K blackbody source.


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## Canuke (Jun 6, 2015)

lyyyghtey said:


> In many cases I would want a pinker source than incan, for romantic appeal or whatever, to the point of adding filters to an already pinkish LED (perhaps for an eating area). When trying to blend in with existing incans where the sources are visible, or where yellow/green colors need to be prominent (lots of plants to look at perhaps), I would prefer a yellower overall tint. Though granted, not often yellower than incan.
> 
> With all these LEDs being 90+ CRI, any of them used by itself would satisfy my needs well. In fact I seriously doubt I'd mind using them side by side in many instances. They really all seem to be very good! I'm just finding it interesting and theorizing why I have yet to find a blue-pump warm source that mimics incan in terms of both yellowness on a white surface, and appearance of a deep red surface, at the same time. You could say I am overly focused on deep red given the rarity of true deep red materials and I concede that it's just a personal preference at that level. But deep red does affect somewhat how other reds appear since most red material i've ever tried responds over seemingly the whole range of red.



Very interesting! It sounds like you look at light and color the way I do, and you notice the same things.

In my case, I have also found that I have a "pink" bias for LED sources by comparison to incandescent/blackbody, at least at the warm end. If an 80 CRI LED has the exact same apparent tint as incandescent, the net result in lighting a scene is what I would term as "thin" or "gutless", almost the visual equivalent of a lack of bass in a sound system. It just seems less "full". Objects or substances that are naturally red/orange - my most notable example of this is cabernet franc icewine from Inniskillin - take on an orange-brown cast in that light, looking like it's been aged too long, but under incandescent, it takes on a richer red quality. I have three warm-white XPG Quarks from FourSevens and one HCRI Preon; the latter is on the yellow side and despite being HCRI suffers from the "thinness" more than the three regular warms, which all came in on the pink side.

Conversely, when I find a pleasing warm-white LED source, it invariably turns out to be on the slightly pinkish side when I compare it to an incandescent source. LED seems to benefit more from the neodymium glass yellow notch filter (as in the first-gen Cree TrueWhites) than does incandescent. So, like you, I would probably find a tension between incandescent-accurate *tint* versus incandescent-like *quality*, and I too think it's the missing deep reds that do it.

High CRI is definitely showing up in the market place more now; you know it's going mainstream when all the Feit bulbs at Costco now sport 92+ CRI claims.


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## toastystuff (Dec 7, 2015)

Could I use these leds in an a2 aviator? Would they tint shift if I were to use rechargeable batteries?


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## purduephotog (Dec 7, 2015)

I bought 2x100 of the 6500K and 2700K 5730 package LEDs for projects. I love them- and while I agree it would be 'nice' for Cree to do it, I've been begging them for years and they haven't. In fact, they provide spec sheets stating 90 CRI @ 6500K with lower L/W, but never produce the item.

So I'll take this triple phosphor LED anyday. I'm just having a heck of a time finding MCPCbs that are not 2x parallel and finding appropriate driver circuits. Settled on 3x in series with an LM317 SOT. Just trying to learn Eagle to make a new package to get quotes on getting some FR4 fabbed for testing and some MCPCB aluminum for no heat sinking.


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## evgeniy (Feb 1, 2016)

Anders Hoveland said:


> Yes, this is indeed true. I have a Yuji violet-pumped LED. The overall color of the light actually appears a just a little greenish-tinted– at least compared to any other LED I have seen– but not really in an all bad way. The color rendering is completely perfect, fully saturated reds and emerald greens, deep indigos and azure cyans. The color temperature is rated 5000K but the really weird thing about it is the light almost feels much more like halogen than any 3000K regular LED I have seen—basically it feels like what halogen light would look like if it came in a higher color temperature.



You buy it on Yuji site ?


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## evgeniy (Feb 1, 2016)

Independent amateur measurements on dpreview.com forum (? custom-made spectrometer?) _Results [for other lamps] from this user are in good agreement with other measurements, and with datasheets. 
_
Yuji High CRI Bulbs [post from _[URL="http://www.dpreview.com/members/9132903746"]Scottie Wang_]

"[/URL]Incredible results!!
It's not cheap and not as bright as regular LED bulb

5600K:750 LM

3200K:515 LM"


VTC 3200K :














VTC 5600K :


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