Wurkkos

High CRI and its significance

TTGV

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Hello,
Does anyone tried to melt the light from a neutral XP-G and a warm XP-G ? The curves made with relative radiant power versus vavelength show two different "top of the hill" for them. It should give a smother curve, more "complete" than each solo one.
I expect to keep a good lm/W ratio...:ironic:
 

Okin

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I would also be interested in hearing what people thought of mixing warm and neutral XP-Gs.
 

Tally-ho

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IMHO concerning lights, it's better to see (by oneself) than to hear. :whistle:

Simple: join the next flashaholics meeting/gathering and ask neutral and warm XP-G's owners to shine different objects with different flashlights at the same time.
 

McGizmo

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Hi guys,
I figured I would dredge this thread back up from the dusty basement as the discussion of tints, CRI and color temperature is still on going and I believe with just as much confusion due to the complexity as always. In the post above, the terms neutral and warm are used. To what do they refer and can they be better defined so that we all have the same idea of what neutral and warm are? I realize that some LED manufacturers bin their LED's as neutral or warm but knowing this, do we have any certainty that A LED will produce light as expected?

I think for most of us, the litmus test is pointing a light at a white surface and making a determination of what the light's output is like. For me I think I inherently interpret cool - neutral- warm based on a one dimensional line going from blue into white and then into yellow. This is pretty much akin to traveling on the Planck curve from high color temperature to low color temperature. Unfortunately LED's are not restricted to the Planck curve and their integrated spectrum may land on a point well off the curve. With LED's we ask what the color temperature is and use the CCT as an answer.

But, from wikipedia: "The correlated color temperature (Tcp​) is the temperature of the Planckian radiator whose perceived color most closely resembles that of a given stimulus at the same brightness and under specified viewing conditions"

Knowing the CCT of a LED does give us some real information but doesn't tell us with certainty what we will see on the white wall.

The CRI of a LED also gives us some real information but it is also an oversimplification of a much more complex and two dimensional realm reduced to a single number. As discussed in this thread, it is based on a black body source and again, the LED is no such thing. The stated CRI of a light source is an average of a number of CRI measurements based on different spectral points and how these compare to a black body source of the same color temperature.

It's been my experience that looking at a white wall for any length of time with any of the contemporary "white" LED's, in no time I can compensate for the immediate perception of any tint and actually recognize the white wall as a white wall. I would add that that first perception of tint is based on the previous light source that my eyes had become accustomed to and that this initial perception is a relative perception. But taking the LED out in the real world and illuminating various colored objects at various distances and resultant levels of intensity, some LED's do a better job than others in providing me with "accurate" information. This accuracy can be a function of color rendering (related to CRI) or it can be a function of what I'll call resolution or acuity which is based on flux and lux more than color.
 
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Bullzeyebill

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But taking the LED out in the real world and illuminating various colored objects at various distances and resultant levels of intensity, some LED's do a better job than others in providing me with "accurate" information. This accuracy can be a function of color rendering (related to CRI) or it can be a function of what I'll call resolution or acuity which is based on flux and lux more than color.

I too have noticed, at distance, that resolution and acuity can be enhanced using low CRI LED lighting compared to Incan lighting, or for that matter Hi CRI LED lighting that does not attain high flux, or Lux, when you increase the flux, and or the Lux of low CRI LED. Saying that, I have also found the reverse to be true, that lower flux using an Incan or a HiCRI LED is very useful for accuracy particularly when identifying colors.

Relative to color acuity, I'll use a basic example. I have some dark brown socks that I can not identify as dark brown socks when I turn on a low CRI LED flashlight to any brightness level including its highest flux possible, even 1300 lumens, and that at a few inches from the socks. Now I know that sock hunting early in the morning is not a big deal, but it is to me when I'm getting ready for church, and forgot to lay out my socks the evening before. I have no problems at all using Incan lights or Hi CRI lights from 3500-4500 CCT. In conclusion, I'll go with Hi CRI LED lighting for just about any purpose, and look forward to higher flux/Lux HI CRI lighting for distant accuracy.

Bill
 

BigHonu

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Bill,

Regarding the color brown and my ability to recognize it using LEDs in general is similar.

I think Don and I may have similar eyes and that how I initially perceive color is dependent upon what light source I was using previously. Still, my brain will readily adjust to the new light source, as long as it is not the aforementioned brown color using an LED source.

So, it seems FOR ME, incandescent sources are preferred when I need to know what color something is. I may not get the color spot on, but I won't be too far off either. Otherwise, LEDs are in my pocket the great majority of the time.


Sent from my HTC One using Tapatalk 2
 

McGizmo

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BigHonu, :wave:

I am curious if you have tried a high CRI LED source in identifying brown. I am curious enough that if you haven't I would be game to toss one over to your island for evaluation purposes and I'll pick up the cost of you tossing it back.
 

BigHonu

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Hey Don!

Short answer is 'no'. I have not used a high CRI LED in any capacity, though have seen some beams from 'warm' LEDs, and have one light fixture in our house that has a commercial 'warm' LED bulb.

Are you kidding me?! I would love to take a look at one of your lights with a high CRI LED, but as long as I can pay for the shipping both ways. Let me know what shipping comes out to and I can shoot you a PP payment.

Thanks!
Brian
 

dc38

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I've been wondering for a while...does the UV spectrum have anything to do with improving CRI? I was curious because there is UV in regular sunlight, which would be the most natural and "neutral" light available. This may be dangerous to put into production if it IS true, but it would be interesting to find out...
 

BigHonu

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dc38,

I'm leaning toward the lack of reds in the light emitted by LEDs. If you can get that in there, it would work out great. I'm no scientist, and I'm sure someone much smarter than myself should be along to correct me.
 

bshanahan14rulz

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As I understand (edit: and as mentioned numerous times in this thread >.<), the CRI index that we use is an average of how accurately a light potrtays a collection of 16(?) colors. I don't know how they turn that idea into a number, though. Something like, "This light portrays this yellow 93 units worth of yellowness." You could make a custom source with only the wavelengths required to render those 16 colors accurately, and it would have a CRIa ~100, but it wouldn't be full spectrum like sunlight.

But, yeah, one common thread I've seen is the ability to show browns in their true brownness. I would guess that this would be of immense importance to folks who spend a lot of time outdoors. Whereas before, many different tints of brown would show up dark gray under my other LED lights, I have a high cri LED light that gives no doubt that they are different hues of brown. I was actually surprised to see that my walls were actually a light brown, not a dirty white. (paint, not dirt, I swear!) For comparison, a Q3 5A XR P60 dropin I made also shows the wall as brown, but not exactly the "right" brown, maybe too brown almost. BigHonu: you will be blown away by high CRI if you are used to using LED lights. I bet next year it will be all the rage for marketing high end LED bulbs. I think this year, we're still in the "efficient, new, and inexpensive" phase ;-)

dc38: I think the only way UV could impact a light's CRI is if the UV caused fluorescence in the visible range. But yes, I could see that affecting it, but I think it would only improve CRI rating if the colors used in the test were made using fluorescent pigments. But you'd be amazed how many things fluoresce to some degree.
 
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McGizmo

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CRI is based on a number of specific bands of visible light and has no bearing on invisible bands. On an interesting aside, the Nichia rep told me a few years back about a Nichia experimental LED that they were developing for potential use in automobiles was a UV LED with a phosphor coating to generate white light. Apparently a UV LED does not have the spectral shift at various V-in like a blue LED does. The major concern was should the LED or its envelope be damaged, it might spill intense UV light out and cause damage to peoples eyes. The advantage was that it would produce the same light at various temperatures and such; be real consistent.
 

bshanahan14rulz

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On an interesting aside, the Nichia rep told me a few years back about a Nichia experimental LED that they were developing for potential use in automobiles was a UV LED with a phosphor coating to generate white light. Apparently a UV LED does not have the spectral shift at various V-in like a blue LED does. The major concern was should the LED or its envelope be damaged, it might spill intense UV light out and cause damage to peoples eyes. The advantage was that it would produce the same light at various temperatures and such; be real consistent.
I remember GE was working on a similar LED. Interesting to note that the wavelength is more stable in a lower wavelength GaN device. I can think another reason for using a short wavelength is that frequency downconversion of phosphors will allow the possibility of keeping with standard phosphors but potentially be able to theoretically fill in the entire spectrum of visible light with downconverted photons from phosphor, whereas typical LEDs the light emitted from the phosphor must be higher wavelength than the originating photon.
 

kaichu dento

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...the lack of reds in the light emitted by LEDs.
I think you're in for a surprise with the light Don is sending you and all it takes is shining on a variety of objects with reds, oranges, greens and such to realize that LED's are no longer what they once were - they have arrived.
 

BigHonu

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Hi Don,

I got the light in last night, but I couldn't get any quality time in. I'll take a better look tonight. Thanks!

Sent from my HTC One using Tapatalk 2
 

McGizmo

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Hi Brian,
No rush and no worries.

I sent Brian a High CRI Mule AA for evaluation. I suspect this is not a light Brian would choose for himself but I think it an ideal light for evaluating the color rendering of the Nichia LED. This is the light I would give to a family member or friend who is not a flashaholic or inclined to carry a light around with them. The AA battery is common and plenty options for primary or rechargeable out there. As for a portable light source, I think a flood is typically more suited to the average person needing to shed some light on what is at hand as opposed to at a distance. Having superior color rendering is a bonus and often quite helpful; for you guys who wear socks anyway. :nana:
 

Bullzeyebill

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Hi Brian, Having superior color rendering is a bonus and often quite helpful; for you guys who wear socks anyway. :nana:

LOL. I always knew you guys over there didn't wear socks. Got to talk to one of my friends, over there, who also snorkels, and enjoys the good life, if he goes sockless.

Bill
 

BigHonu

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First off, I would like to thank Don for letting me take a look at his High CRI Mule. I received the 1AA based Mule last week and have been using it as my primary light.

My lights

As Don noted, most of the lights I have on hand are geared for longer range outdoor use so I needed to make a conscious effort to make sure anything I was seeing as not based on a difference in the amount of light on an object/scene.

Color temp of lights I already have goes from the slightly yellow end of the spectrum to cool blue.
Most of the following issues I have with the LED based lights I own come from the bluish tinted beams. The slightly yellow beams see some of the same issues but to a lesser extent.

With current lights, all browns become harder to differentiate the darker the brown gets. Stained wood grain becomes muddled, and objects at a distance (branches in a tree or a toad lying amongst rocks) will become featureless. Yes, I have picked out brown socks out of the drawer thinking that they looked black at the time.

Greens up close (grass, leaves, moss, etc.) will shift over to a more blue hue. When overall lux drops due to distance or fog/vog/sea spray, the greens will tend to smear, lose texture, and get lost into any darker surrounding colors.

Any neon, orange, purple, and certain blue colors will pop more than usual, almost as if they reflect a good deal more light than their surroundings.

The High CRI experience

The easiest way for me to describe the high CRI Nichia beam was that no color stood out, and that was simply AWESOME. I’m so used to flipping on a light, and some color will immediately jump out or get washed out. With the Nichia, nothing looked unnatural. Everything was as it should be. From a color rendition standpoint, it is the best I have seen out of ANY portable light source.

The only thing I wrote in my notes that can be deemed a minor negative is while looking at something ‘weathered’ such as a faded shirt or an old board that has been sitting outside. I lose a smidge of the weathered effect, and colors actually look better (i.e. less faded) than they would under the sun.

With regards to my color nemesis with LEDs, the Nichia produces the most natural looking browns I have seen. No unnatural darkening or color shifts. Wood grain looks sharp with good contrast, and most importantly, I can easily tell the difference between my socks. Even the different shades of brown ones.

I apologize for not including more quantitative data, but for me, the light simply works.

Everyone has their own priorities for portable lighting, and until last week I thought I had most of my bases covered. I knew the limitations of the lights I normally carried and I was okay with them. The high CRI option in Don's light has opened my eyes to what an LED can do and has prompted me to start revisiting my lighting priorities. With the Nichia, I can see and identify what I need to without being distracted at some level with what the beam is showing me. One of the first times that has happened to me in a LONG while, and has re-ignited my waning interest in lights.

Brian
 
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