Debunking that Low CRI is brighter than High CRI... not necessarily

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jon_slider
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Debunking that Low CRI is brighter than High CRI... not necessarily

How less OTF lumens can produce a brighter hotspot than more OTF lumens..

the secret is the size of the hotspot
smaller hotspot can be brighter than larger hotspot

these two lights are Jetbeam Rotaries running 18350 LiIon:

the hotspot of the HIGH CRI is 15% Brighter!
even though the xml is 46% brighter out the front.. the lumens are diluted over a larger area

Edited by: jon_slider on 07/28/2020 - 17:30
Th558
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This doesn’t make sense cause they’re two different emitters with different die sizes.

longuylander
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That’s why lights’ outputs are also measured in candela/throw.

buck91
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Ummm, right…

Firelight2
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Usually, but not always, high-CRI comes at the cost of lumens.

Warmer color temperatures mean more phosphor on the LED die, which means lower output. A 6000K LED typically produces more lumens than the same emitter in 3000K. Couple that with most high-CRI emitters being towards the warm side of the spectrum and the reduction in lumens with CRI is evident.

Also, if a manufacturer is sorting emitters by bin and choosing the ones with the best possible CRI, those chosen might not have the highest possible output.

Some common high-CRI emitters like the E21A and Nichia 219B have great CRI, but incredibly low output compared to lower CRI options like XPL HI.

There are some exceptions though:

  • CREE makes some high-CRI XHP 50, which are found in some Zebralights. They have excellent output and great CRI.
  • SST-20 is an excellent high-CRI emitter. Output and throw is still less than lower-CRI XPL HI, but not by a huge amount.

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Completely different emitters, not a valid comparison.
If you look up how lumens work you will see that the highest efficiency is at 555nm monochromatic green light.
So for an LED that uses a constant amount of power you will get the highest lumens with a 555nm green LED which is essentially 0 CRI.

Also, more relevant to the average flashlight user who wants white light, if you compare white LEDs of the same manufacturer, series, and model, you will see that the high CRI variations always have lower flux bins and lumen output and often consume more current and produce more heat.

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Enderman wrote:
Completely different emitters, not a valid comparison.
If you look up how lumens work you will see that the highest efficiency is at 555nm monochromatic green light.
Isn’t that where our eyes are most sensitive?

That’s not necessarily what’s most efficient for LEDs though.

A white LED consists of a blue LED with a layer of yellow phosphor on top. When the blue light hits the phospor, some passes through, while some is absorbed by the phosphor which then emits red and green light. The overall output consists of red, green and blue light which combines to create white light.

The thicker the phosphor, the more red and green light you get and the warmer your overall color temperature. However, no process of light conversion is 100% efficient. Some energy is lost when blue light is converted to green or red. The result is that for the same LED, warmer color temperatures almost always produce less lumens.

Also, my understanding is that when LEDs are manufactured they come out of the factory in various different tints, output and CRI. A machine then sorts and bins them based on things like color temperature, output, and CRI.

Not surprisingly, the ones sorted primarily for CRI do not typically have the highest output.

jon_slider
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longuylander wrote:
That’s why lights’ outputs are also measured in candela/throw.
agreed!

throw is not just based on Total OTF, it accounts for the focus of the beam

.

Th558 wrote:
they’re two different emitters with different die sizes.
correct.. that IS the point Smile
smaller hotspots are brighter than larger hotspots

When I upgrade a low CRI larger die
to High CRI on a smaller die

I win!
I get both a brighter hotspot, and Higher CRI

It seems counterintuive because the Total output of the Low CRI is more lumens out the front

It actually makes total sense, that a more focused hotspot can have a brighter center, than a wider more diffused hotspot

and it gets better
a triple with LOTs more lumens is not necessary brighter on target than a single with less total lumens

again the critical distinction is the brightness on the target within the hotspot

it actually takes many more lumens out the front of a triple, to match the brightness of the center hotspot on a target, illuminated by a more focused and smaller hotspot…

this conversation goes beyond just total Lumens out the front.. it involves the illumination on the target.. aka LUX

see if this helps:

the narrow beam is 10X brighter than the wider beam.. its all about the size of the hotspot.. it matters More, than the OTF output

longuylander
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As I said… this is why output is also measured in candela.

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I think jon_slider’s point is more relevant to a discussion of “lumens” vs. “lux”. It doesn’t really have anything to do with CRI at all.

In your example of an RRT-01 with Nichia219B having a brighter hotspot than with the stock XML … yes that’s true. But if you’re swapping out emitters, you could swap in a throwier one like an Osram White 1 or White 2 and have a much, MUCH more intense hotspot than the Nichia 219B.

The result is you’re still sacrificing hotspot brightness to get high CRI.

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I think most people here understand the difference between lumens and lux, as well as the tradeoffs of optimizing one over the other.

But that seems quite unrelated to high cri vs low cri, so I’m not sure I understand the point of the thread.

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Random Dan wrote:
I’m not sure I understand the point of the thread.

I will try to explain.

I recently received an RRT-01 that needed a broken wire repaired. The owner did not want me to upgrade the LED to High CRI, because he has the typical belief that High CRI makes less total lumens, which is true.

It really bothered me to ship out a Low CRI light, but I respect that different people have different priorities, based on what they believe to be true.

as far as I can tell, the Low CRI does have more total lumens, and a wider hotspot, that is less bright in the center, than the High CRI LED.

it appears to me, that marketing of Lumens out the front, has left many people unaware of the concepts of Lux and Throw..

the point of this example is to offer some alternative facts.. that is

the SW45k produces a smaller but brighter hotspot on target
than the xml that produces more total lumens out the front, but spreads them over a larger area, resulting in an actual lower brightness on target, in the hotspot.

most people, myself included, are not as aware of Lux and Throw as Lumens.. possibly because marketing touts Lumens, and does not provide Lux and Throw data.

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Firelight2 wrote:
* SST-20 is an excellent high-CRI emitter. Output and throw is still less than lower-CRI XPL HI, but not by a huge amount.

What’s really cool is the 70CRI 5000K SST-20, which does out-throw XPL-Hi. And further reinforces the “CRI costs lumens” thing

EDC Rotation: ZL SC62(w) | Jaxman E2L XP-G2 5A | Purple S2+ XPL-HI U6-3A | D4 w/ Luxeon V | RRT-01 | Purple FW3A, 4000K SST20
EagTac D25C Ti | DQG Slim AA Ti | Jaxman E3 | UF-T1 by CRX | Nitecore EX11.2
L6 XHP70.2 P2 4000K FET+7135 | Jaxman M8 | MF02 | Jaxman Z1 CULNM1.TG | Blue S2+ w/ ML Special
Unfinished: Supfire M6 3xXHP50.2, Sofirn C8F, Sofirn SP70
Others: Nitecore EC23 | Nebo Twyst | Streamlight ProTac 1AA | TerraLux LightStar 100

jon_slider
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CRI does cost lumens

but in this case, it did not cost Lux

The High CRI sw45k with less Lumens, ended up having more Lux than the Low CRI xml that has more lumens..

I think thats really cool!

next time somebody tells me they want the most lumens possible, and therefore do not want High CRI, I may be able to show the High CRI option actually has more LUX

I dont think most people have been exposed to Lux Education enough to understand it, yet.

This is my attempt to spread an understanding of LUX in order to dispell the Myth, that a Low CRI LED will be brighter on target, than a High CRI LED.. not necessarily.. and not in the example I posted above

part of the problem is Lux and throw specs are not always part of the factors that a buyer considers.. sometimes only Lumens are considered when choosing a light

the typical assumption is that more Lumens means more Throw.. but that depends on the size of the hotspot

maybe this will help too

longuylander wrote:
this is why output is also measured in candela.
yes
unfortunately, there are no specs listed when I modify the light to a different LED
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I see you discovered the difference between “lumens” and “throw” jon_slider. Grad

One other way to consider the difference is a simple test you can do with different lights.

  • To compare the lumens of two different lights – go into a bathroom and close the door. Hold one light in each hand. Tilt your head down and look at something on the floor near your feet. Hold one light above your head and point it at the ceiling and turn it on. Then turn it off and repeat with the other light all while keeping your eyes on the object on the floor.

The trick with this test is the hotspot of each light is not in your field of vision at all. Instead, all you see is diffuse reflected light that bounced around the room and got to the object around your feet. If one light makes that object light up noticeably more, it probably has higher lumens. Note however, for the difference to be visually noticeable there typically needs to be at least a 20% difference in lumen output.

  • To compare the lux (throw) of two different lights – point each light at the nearest wall and compare the hotspots. The one with a more intense (brighter) center of the hotspot has better throw. To get a better idea of which one has more throw, try pointing your lights at a dark object. Or just wait until night and point it out the window at something off in the distance.

Note also modding to high-CRI doesn’t necessarily mean you get more throw. In the case of your old RRT-01 with XML vs. Nichia 219B SW45K… yes, the Nichia has more throw. But in many cases low-CRI leds have more throw. For example the following low-CRI 3v LEDs all easily outhrow SW45K: SST-20 5000K, XPL HI, and Oslon White 1 or 2.

jon_slider
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Firelight2 wrote:
I see you discovered the difference between “lumens” and “throw” jon_slider. Grad
yes, and
its more than that

I discovered that High CRI can have more throw than Low CRI

Firelight2 wrote:
To compare the lux (throw) of two different lights* – point each light at the nearest wall and compare the hotspots.
yes
that is what I did.. I put the sensor of my light meter in the middle of each hotspot, on the wall

I show the results of that measurement in the photos in the first post

the High CRI LED with less lumens has a smaller brighter hotspot, than the LED with more lumens

I get to have cake and eat it too
high CRI and a Brighter hotspot

next time somebody tells me they want to keep the Low CRI LED because it has more lumens.. Im going to show them the High CRI can have a brighter hotspot.

beam size matters

jon_slider
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ToyKeeper just pointed out that the hotspot of a single LED is five times brighter on target than a triple LED.

ToyKeeper wrote:
Efficiency, as measured in candelas per Watt, is usually higher with just one LED. … Take the FW3A vs FW1A as an example. The single-emitter version is … illuminating its target about 5X as bright.

the reason for this is that the single LED is producing a more focused hotspot. Whereas a triple spreads the lumens out over a wider area.

ToyKeeper wrote:
Basically, do you want an extreme flooder at ~2 cd/lm or a balanced beam at ~10 cd/lm?

this is about how much more brightly the target is illuminated by a small tight beam from a single LED, and how much wider, but dimmer the illuminated area is when using a triple.

The single LED is brighter on target because the light is focused into a smaller area. The triple makes more total lumens, but spreads them out over a larger area, so the brightness on target is lower.

jon_slider
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longuylander wrote:
lights’ outputs are also measured in … throw.

I found an off the shelf example,

thanks for your help pointing out that the difference between Total Lumens out the front, and Lux on target,

can be found on the packaging of stock lights:

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Tighter beam pattern doesn’t mean more lumens or more otf, it’s more throw. Thats why am LEP flashlight at 500 lumens can out throw the 32000 lumen flashlight. Tightness of hotspot, vs spill and flood

Smaller emitter will always win in the same size reflector, use two of the same size emitters in different tints is the only way to run your test.
I feel trolled by this post

I’m glad I’m not the only flashlight collector out there, I was beginning to think I was strange.
My name is Kendall and I’m a Flashaholic from western Canada

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Brightness was one of the reasons I used a SST-20 in the Fitorch P25. Got rid of ugly tint and gained some beam distance. I love it when a plan comes together.

jon_slider
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Unheard wrote:
I love it when a plan comes together.

me too!
I figured out how to get High CRI with more throw, than Low CRI that has more Lumens but less throw

another example of more lumens with less throw
the difference is due to the size of the hotspot:

buck91 wrote:
Ummm, right…

Smile

have I managed to explain in a way you can understand now?

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Firelight2][quote=Enderman wrote:
The thicker the phosphor, the more red and green light you get and the warmer your overall color temperature. However, no process of light conversion is 100% efficient. Some energy is lost when blue light is converted to green or red. The result is that for the same LED, warmer color temperatures almost always produce less lumens. Also, my understanding is that when LEDs are manufactured they come out of the factory in various different tints, output and CRI. A machine then sorts and bins them based on things like color temperature, output, and CRI. Not surprisingly, the ones sorted primarily for CRI do not typically have the highest output.

 

It's not the thickness of the phosphor layer (alone). High CRI LEDs feature completely different phosphor mixtures to achieve that better light quality.

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Your explanation is clear, but the topic of the thread causes confusion:

Quote:
Debunking that Low CRI is brighter than High CRI… not necessarily

Here’s why:

  • When we hear the term “brighter” we think of lumens. Your example in the original post is wrong: SW45K is not brighter than XML. The XML produces more lumens (around 500) compared to the SW45K (maybe 250).

  • The “lumens versus lux” debate is something most of us are familiar with. As flashaholics we know that lumens is not necessarily correlated to throw. Throw is mostly governed by the intensity of the emitter and width of the head. Usually small intense LEDs like Osram White 1 in single-emitter setups with huge wide heads give the best throw. In contrast, for the most lumens you generally want lots of LED die surface area. Typically this means using large LEDs like XHP 70 or XBT 90, or multi-LED setups.
  • CRI is a separate issue…. it’s not part of the “lumens versus lux” debate at all. Most high-CRI LEDs produce less lumens and/or throw than available lower-CRI alternatives for the same light, but that’s not a hard and fast rule.

A better title might have been “I was surprised that my high-CRI LED had more throw than the original low-CRI LED

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Congratulations, you just “discovered” the concept of Lux. Intro to Light 101, 2nd day. Tomorrow, CCT! Grad

Throw != brightness

I agree word-for-word with every single thing Firelight2 has said.

.
.
.
edit: I see I even used the same verbiage as Firelight2 used in post #15, I swear I didn’t do that on purpose, lol.

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Around the house, I normally just grab my WW Xeno E03 (to distinguish it from the 40 other “E03“s out there) with diffusion film on front glass. Great smooooth wall of WW light, perfect for poking around down the basement without having to turn on all the lights in existence.

T’other day, I forgot where I put it, so grabbed my GTmicro to go down there. Ugh, it was nigh useless, even cranking it up to stoopit-bright. Intense hotspot, could’ve used a laser-pointer for what good it did me. Everything else was dark, washed out by the blinding-bright hotspot. And dark-brown paneling all over (even the ceiling; it is a basement, after all), so I couldn’t even use ceiling-bounce for light.

“Bright” ain’t all it’s cracked up to be. Just use the right tool for the job.

09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0

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So yes if I can get hi cri that out throws a cool white emitter in the same form factor (host) yes I’ll go hi cri almost every time.

I’m glad I’m not the only flashlight collector out there, I was beginning to think I was strange.
My name is Kendall and I’m a Flashaholic from western Canada

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A lot of hair splitting here. I perceive a spot of high luminance as bright.

I think it’s clear what Jon means. No?

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thank you all for helping me to learn how to communicate more clearly

the brighter smaller hotspot on the right:

is not from the light with more total lumens out the front,

and it is also not from the light with more emitters

the light with more Total lumens out the front, and more emitters,
is not more efficient at producing a bright hotspot

because the extra lumens and extra emitters create a larger, dimmer hotspot, the triple needs to use more battery power to match the brightness of the smaller, more power efficient, and brighter on target, hotspot.

So Im debunking three myths
1. with more lumens I can see farther outdoors
2. triples are more efficient than singles, at letting me see farther outdoors
3. Low CRI is going to be brighter on target than High CRI

what is actually true is
1. smaller hotspots let me see farther than larger hotspots do
2. single LED lights use less battery power, to let me see farther, than multi LED lights
3. The Low CRI xml in my stock RRT-01m produces a larger hotspot, which is not brighter on target, than the HIGH CRI sw45k in my modded RRT-01, that has a smaller hotspot

So, I think I might buy an FW1a with High CRI and less lumens, instead of an FW3a or D4 with Low CRI and More Lumens,

So I can enjoy an efficient, small, bright, High CRI hotspot..

and instead of focusing on the Lumens specs..

I will focus on the throw specs Thumbs Up

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1. Who ever thought that just because a light has more lumens that it would throw farther?
2. Triples are more efficient, and again, there was never a claim that they throw farther (in fact, the opposite has almost always been the rule).
3. * CRI has nothing to do with the brightness of the hotspot.*

Why are we still discussing the fact that a light with a smaller hotspot will also have a brighter hotspot, when other factors are close to similar? Yes, even if a light has more lumens, the center of its beam may not be as concentrated as a light with less lumens. My Convoy C8+ with an xp-l hi, putting out 1100 lumens is far brighter on a point than my Lumintop EDC18 with three of the same LEDs, putting out 2800 lumens. But the C8+ is nowhere near as useful or versatile. Rarely do I need such a bright spotlight that can throw as far as the C8+ (I call it the dog finder, for when my min pin escapes from the yard). If I wanted to use it on its lowest setting indoors, I’d be constantly sweeping the light back and forth to see things in that tiny spot. Regardless of whether I need a floodlight or a spotlight, the lower CRI LEDs will more likely have more output than high CRI LEDs in the same setup. That sacrifice of power for color rendering is always a consideration in any light, just like one’s preference or need for flood vs. spot. Please stop comparing, combining, and confusing the two.

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Very good points, Jon_Slider. It’s about picking the right tool for the job.

For seeing off in the distance a light with a small hotspot is great. I have an Eagtac T25C that I modded with an Oslon White 1 and a FET driver. Throw on a 16340 is amazing for such a tiny light. But up-close I find it largely useless. The hotspot is tiny and so blindingly bright it washes out the spill. And due to the deep reflector the spill is quite narrow.

For a pocket EDC that is used mostly at close-range small triples and quads work great. their wide even hotspot is excellent for lighting up a large area up close, and with a FET driver and good cell they have enough power to punch out a fair distance just through brute force … but without that kind of high output driver they’re much less impressive.

I get what you’re saying about triples though. For years my Jetbeam TCR-01 was setup as a triple XPL HI. I wasn’t EDC’ing it though, because the output didn’t really satisfy. Overall output seemed quite low, probably because I was used to FET drivers and larger batteries in my FW3 and D4 series lights.

I recently refurbished my TCR-01 by converting it back to single-emitter with an OP reflector ….. much better. The hotspot gives it respectable throw and the spill is bright and wide enough to be useful. Overall an improvement compared to when I had the light setup as a triple.

CRI? … If I can get high-CRI without sacrificing lumens, throw or tint it’s always better than low-CRI. My 2020 RRT-01 was greatly improved by replacing the stock 70 CRI 219C with a 90 CRI 219C salvaged from an EDC18.

jon_slider
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Firelight2 wrote:
I recently refurbished my TCR-01 by converting it back to single-emitter with an OP reflector ….. much better. The hotspot gives it respectable throw and the spill is bright and wide enough to be useful. Overall an improvement compared to when I had the light setup as a triple.

similar personal preference
I use my TCR-1 with sw45k as EDC more often than my RRT-01 with triple sw45k.

I find the triple less useful for general EDC and it gets carried less. It also seems dimmer on target, unless I turn it up to a much higher total output level, which consumes batteries faster.

otoh, the triple is more useful when I want to use it as a light source for a photo..

the single in the TCR-1 battles with my camera light sensor, and I cant get an evenly lit photo.

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