# Looking for high CRI LED



## BlueFusion (May 4, 2011)

Hi all,
I'm looking for an extremely high CRI LED for measurement/testing. Since I only need low power, I've been looking at low power LEDs but haven't found any with a CRI above 87. There are some Seoul high power chips which have CRIs in the 90s but I don't know if they retain their CRI at low drive currents.
Can anybody suggest anything suitable to use, and more importantly where to get it? Somebody had some amazing Nichia 97 CRI ones but according to Nichia's site they don't officially exist and they seem to be literally impossible to get.
Thanks


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## videoman (May 4, 2011)

You can check out Cutter Electronics in Australia. See the Cree XP-G in the 90 CRI category 2700K ish. http://www.cutter.com.au/products.php?cat=Cree+XPG


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## BlueFusion (May 5, 2011)

Wow - wasn't aware the XP-G came in high CRI bins. Awesome, thanks.
Just to confirm - it does keep its CRI at low drive currents, like under 350ma?


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## srfreddy (May 5, 2011)

There were Nichia for sale on the Marketplace last time I checked.


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## LEDAdd1ct (May 5, 2011)

Yes, Travis (Tekno_Cowboy) has some very nice Nichia's for sale. He put one in an HDS Twisty for me, and it came out beautifully.

I would ask Travis in the sales thread if it would meet your needs, as he knows his stuff and he certainly knows the LED he has for sale. :thumbsup:


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## SemiMan (May 5, 2011)

I think you have not guarantee on CRI with low drive current on any high powered LED. However, you could do one of two things:

1) PWM -- I.e.. pulse them on and off. Is that an options for what you are doing?

2) Use a neutral density filter ... proper optical neutral density filters will not impact the spectrum if used properly.


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## calipsoii (May 5, 2011)

LED's shift tint as you lower the current that passes through them. All datasheets will have a graph that will show amperage vs. CIE coordinates.

The only way to guarantee that an LED will have the same tint at a lower output is to use PWM to drive it less often at full power, fooling your eyes into thinking it's dimmer. Any old PWM driver should be able to do this for you.


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## BlueFusion (May 5, 2011)

Thanks for all the great info - I'll chase up those Nichias as low power is still the way to go if I can help it.
However - my particular measurement application means that high power is still an option. Rather than a full PWM however, it would simply mean a very short on-time while actually taking the measurement I need from my sensor. (few milliseconds)


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## snarfer (May 16, 2011)

Normally high CRI phosphor type LEDs have considerably less color shift when analog dimming than their lower CRI counterparts. I believe this is due to the use of multiple phosphors. 

Additionally, color shift is caused not only by change in applied current but also by change in die temperature. 

Pulsing may therefore be unnecessary, and/or ineffective as a strategy to maintain CRI at lower drive levels, despite manufacturer claims to the contrary.


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## Tuikku (Oct 31, 2011)

Hi!

Are there any options for High CRI LED at around 4500K?
I´m a bit noob on these high CRI´s, so would like to try one. I know I don´t like warmish tints but high CRI with a bit higher temp could be just right for me.

Planning to make a low output dropin, perhaps, so output is not so important.


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