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

This doesn’t make sense cause they’re two different emitters with different die sizes.

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

Ummm, right…

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.

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.

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.


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


correct… that IS the point :slight_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

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

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.

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.

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.

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

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

unfortunately, there are no specs listed when I modify the light to a different LED

I see you discovered the difference between “lumens” and “throw” jon_slider. :student:

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.

yes, and
its more than that

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

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

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

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.

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.

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:

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

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.