5000k Kelvin bulbs with good CRI?

[scamp2112]

My wife is a big fan of the ott-lite CFL's that are friggin expensive and seem to last just long enough to be out of the replacement window. I'd like to transition to LEDs but she is insistent on the "Full Spectrum" daylight type bulbs. Seem's like Philips is the only recognized brand I see that is putting LED's in that color temperature. Seems Philips is well received here as far as LED's go but I'm wondering if there is any other brands to consider. Below is what I am leaning towards as it seems to put out the most light at the temperature she wants but before I spend a couple hundred dollars on bulbs it would be nice to know I am buying a quality product. I don't really care what they cost if they really last 5 years or so and I'd like them to be as bright as possible.
http://www.amazon.com/Cool-White-Di...=dp_db_cm_cr_acr_txt?ie=UTF8&showViewpoints=1

 

[neutralwhite]

4.0 out of 5 stars Not for everyone 11 Feb 2013
By J. Nguyen - Published on Amazon.com
Amazon Verified Purchase
Pros:
- A step up from CFL lighting.
- Use less than half the power of the equivalent luminous bulb.
- Suppose to last longer than CFL bulb.
- Not as fragile as other non-led bulb.
- Don't cause skin cancer/burn like CFL/equivalent bulb (big Plus).
- Suppose to be one of the brightest led bulb as of writing.

Cons:
- Not as bright as CFL bulb, but are bright enough.
- Very very expensive.
- Did I say very expensive?

 

[JaysonM]

Are the bulbs your replacing in Recessed fixtures. Heat will degrade these bulbs rapidly. I don’t have any of the particular bulbs you are considering but I burned out a $39 bulb rated to 820lm in a recessed fixture because it was operating around 165F (according to IR temp gun) all the time. The heat had nowhere to go and I think I cooked it

 

[Anders Hoveland]

Not that they will fit into any of your old fixtures, but you might want to investigate some of the high-end LED reef lamps:

http://ecotechmarine.com/products/radion/

This company offers custom designed LED fixtures. You can choose which frequency LED chips to use in combination to optimise the overall spectrum output:
http://www.buildmyled.com/custom-led-strip/

 

[jtr1962]

This company offers custom designed LED fixtures. You can choose which frequency LED chips to use in combination to optimise the overall spectrum output:
http://www.buildmyled.com/custom-led-strip/

Very useful link. Thank you!

I was playing around with different combinations of LEDs. It turns out in many cases that if you have x lumens of white (5000K to 6500K), you need to add maybe 0.17x of 525 nm, about 0.05x of 625 nm, and 0.02x of 660 nm in order to get CRI well into the high 90s. For warmer white LEDs maybe 10% or 11% 505 nm plus ~3% 660 nm works (no need to add any 625 nm).

 

[Anders Hoveland]

Very useful link. Thank you!

I was playing around with different combinations of LEDs.

I got a good spectrum graph by combining a 470nm blue, two 505nm cyans, a 525nm green, a 625nm red, another 660nm red, and nine 3500K white LEDs.

There appears to be a trade-off between being able to obtain a smooth spectrum and not making the overall light color too magenta colored. If you are okay with a pinkish color of light, you could probably get slightly better color rendering by not using the 525nm green, and only using one 505nm cyan. A 405nm violet might slightly help color rendering also... but that is really a more complicated subject of opinion.

Another option might just be to use a 470nm blue, a 505nm cyan, and a cool white LED to enhance the spectrum of a 3000K halogen bulb.

Just my opinion here, but 505nm is not really "cyan", it is more of a slightly bluish-green, commonly used in some traffic lights now.

"Turquoise" exotic LED chips do exist, emitting at 495nm. I cannot find any information about it, but I suspect it is actually a 405 violet chip with a cyan phosphor, and the efficiency might not be very high. Cree also makes a 465-480nm LED, available as a 30 watt chip. It's more towards the blue end, but not as much as a 470nm blue. I just mentioned this because if the turquoise chip turns out not to be practical or available, the next best thing may be to just use this 465-480nm chip, along with a common 405nm blue-green. There will still be a little gap in the spectrum, but at least it would be narrower.

 

[SemiMan]

It is great being able to mix a variety of LEDs to achieve a particular result, but unless you have active feedback, i.e. what Cree uses in their fixtures, then temperature effects between InGaAn and AlInGaAp, binning variances and different aging rates will eliminate any advantages. With two colors, you can do some narrow band sensor feedback implementations. When you have multiple colors you get into more complex control. Not difficult, just needs to be done.

Semiman

 

[jtr1962]

You might be able to get away without active feedback doing something like I mentioned using mostly white LEDs with a few cyans and reds thrown in if you use good heatsinking. The key is to keep the reds from getting too warm.

On another note, I knew CRI could be negative but I didn't know how bad it could get. Try using 8 730 nm LEDs, 3 660 nm, and 1 470 nm in that app. I get 3464K and a CRI of -322!

 

[jtr1962]

I got a good spectrum graph by combining a 470nm blue, two 505nm cyans, a 525nm green, a 625nm red, another 660nm red, and nine 3500K white LEDs.

There appears to be a trade-off between being able to obtain a smooth spectrum and not making the overall light color too magenta colored. If you are okay with a pinkish color of light, you could probably get slightly better color rendering by not using the 525nm green, and only using one 505nm cyan. A 405nm violet might slightly help color rendering also... but that is really a more complicated subject of opinion.

Another option might just be to use a 470nm blue, a 505nm cyan, and a cool white LED to enhance the spectrum of a 3000K halogen bulb.

Just my opinion here, but 505nm is not really "cyan", it is more of a slightly bluish-green, commonly used in some traffic lights now.

"Turquoise" exotic LED chips do exist, emitting at 495nm. I cannot find any information about it, but I suspect it is actually a 405 violet chip with a cyan phosphor, and the efficiency might not be very high. Cree also makes a 465-480nm LED, available as a 30 watt chip. It's more towards the blue end, but not as much as a 470nm blue. I just mentioned this because if the turquoise chip turns out not to be practical or available, the next best thing may be to just use this 465-480nm chip, along with a common 405nm blue-green. There will still be a little gap in the spectrum, but at least it would be narrower.

Adding just 505 nm, 660 nm, and 625 nm seems to work pretty well actually. For example, if I take 8 3500K whites (CRI 86), then add one 505 nm and one 660 nm I end up with 3709K and CRI 98. I can do nearly well at higher CCTs by taking 10 6500K whites (CRI 78), adding three 505 nm, one 625 nm, and one 660 nm to end up with 6100K and CRI 97. The fewer different colors you use, then less issues with aging and temperature effects.

I've yet to be able to do any better than CRI 98 with any combo, but for practical purposes once you get much above 90 nobody can tell the difference.

EDIT: 8 3500K whites + 4 6500K whites + 2 505 nm + 1 625 nm = 4473K and CRI 99

 

[Anders Hoveland]

Just my opinion, but I think a soft blue frequency LED is absolutely critical to approach an excellent quality of light. Unfortunately, this specific narrow frequency range is rather rare for LEDs.
I also found a 485nm Cree ( XBDBLU-00-0000-000000Z01 ) LED chip. Just combine that with a common 505nm chip, a deep red 660nm, and a few 2700K whites.

I have been noticing more and more, the blue frequency in an ordinary white LED just seems a little "harsh", not quite the same as the blues in sunlight.