Is there a law of diminishing returns when it comes to lumens?

realdog4

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Forgive me for my ignorance, I am new to LED lights. I don't even know if I should refer to the collection of flashlights as a hobby? After all, many depend on certain lighting tools as necessity for a profession. Now to my point:

I recently was in the market for a new flashlight. I read forum posts, watched videos and suffered a bit of sticker shock.

I saw many flashlights with varying lumens. I was interested in two flashlights. One was 600 lumens while the other was 960.

Is there a certain threshold where the increase in lumens becomes minimal?

Could you easily notice the difference from the above referenced figures or are they a true measure of luminosity? (assuming all other components are of equal quality)

Thank you for your time.
 

archimedes

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....
Is there a certain threshold where the increase in lumens becomes minimal?
....

:welcome:

Perceived brightness is logarithmic, not linear .... There are many threads here that discuss the technical factors in great detail (the search box on this forum should be helpful in this regard). To summarize very simply, however, it may take anywhere from 4x-10x lumens to "appear" twice as bright, with all else held equal.
 

TexLite

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Another thing to consider is regulation. Try to find a runtime/output graph of the 2 lights in question. It may well be that the 900lm model might drop in output after a few minutes and end up closer to the 600lm light, if it were better regulated.

-Michael




Sent from my iPad using Candlepowerforums
 

kyhunter1

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Sometimes manufacturer specs are not accurate. Some over-rate, and a few under-rate lumens. (very few). Generally you can trust brands that have a good reputation. For the most part, you get what you pay for. Buy a good quality light and you will cry one time, it will be well worth it for the long haul. Find a few your interested in and do some research. Lots of info on here, and a good reviews section. I would suggest finding a light that has a good balance of output vs. runtime. Regulation is also important, (how well it maintains brightness during it's runtime). I personally don't like a light to initially be very bright, then dim out to a significantly lower output for the rest of the runtime. A good build quality is also a must have.
 

martinaee

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Forgive me for my ignorance, I am new to LED lights. I don't even know if I should refer to the collection of flashlights as a hobby? After all, many depend on certain lighting tools as necessity for a profession. Now to my point:

I recently was in the market for a new flashlight. I read forum posts, watched videos and suffered a bit of sticker shock.

I saw many flashlights with varying lumens. I was interested in two flashlights. One was 600 lumens while the other was 960.

Is there a certain threshold where the increase in lumens becomes minimal?

Could you easily notice the difference from the above referenced figures or are they a true measure of luminosity? (assuming all other components are of equal quality)

Thank you for your time.

My first "good" LED flashlight was a Fenix LD20 xr-e q5 back in 2008-2009. I feel like that was around the time when truly led lights were starting to have a major revolution that hasn't really stopped since in my opinion. Now the ~200 lumens that light put out is pretty common even among stuff you can get at stores like Walmart/Target/etc. but it still is an impressive amount of light when you think about it. No consumer products were really doing that outside of much bigger and more expensive lights even a few years before that. Not small single led lights at least that I know of.

So that's a little preface to assure you that pretty much any light you get right now from Fenix, Surefire, Thrunite, Nitecore, Streamlight(sorta), Jetbeam, Olight, and many more are going to knock your socks off if you haven't had a high quality/high powered led light yet from the past few years. Like archimedes said human perception of brightness is definitely logarithmic *with all things being equal*. If you are looking at several lights all in the 600-1000 lumen range (I'm guessing single 18650 lights) then look more at what kind of throw they have, i.e. intensity/candela. Just taking two random lights that I don't even have, but say you have a Fenix TK22 special edition with an xm-l2 putting out 650 lumens (I think that's about right for that light) and a much smaller reflector light with the same emitter (not necessarily same tint) like the Fenix E35 Ultimate Edition (burst of 900+ lumens) or the Thrunite TN12 2014 edition (1000 lumens max). While technically you are putting out more light with those other two lights (which are actually smaller lights) The TK22 with a bigger head and reflector is going to throw more of those 650 lumens farther and collate the beam so that the center hotspot is literally brighter.

I know it's hard to really see the difference if you haven't been able to play around with a lot of lights, but as a lot of people here will tell you including myself I'd rather have a light with fewer lumens that has a super smooth beam with few weird artifacts (the TK22 actually could do that well as it has a micro textured "orange-peel" reflector) and has a great tint (somewhere between 4750-5250 kelvin personally lol) than a light that's just blasting out lumens but has a weird beam with horrible tint and sub-par build and ergonomics.

What lights are you considering right now? Oh and also don't make the mistake of doing what so many people do including myself when I first started getting into lights: Pay more and get good quality stuff from good brands. Seriously stick with the major brands (some of which I listed above) instead of getting cheaper stuff off ebay or other places that may be using the same emitters. You will quickly notice how much build quality and reliability come into play. You really do get what you pay for with high end lights and you won't regret it. The good news is you can get lights that are awesome starting from 30-40 dollars these days from the major brands.
 
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reppans

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Yeah, I go by the usual square/square root physics laws governing much of the natural world (like wind force, light, sound, kinetic energy, etc). All else being equal, it'll take about 4x the lumens (and 4x the battery energy) to appear twice as bright. The same laws of diminishing returns works in reverse too though - if you go down in lumens, you attain increasing gains. So for every half reduction in perceived brightness you can live with, you'll get about 4x the runtime. The later has turned me into a sub-/low-lumen, night vision junkie ;).

In your example, assuming beam profiles are identical, I would estimate 960 lms would appear ~ 27% brighter than 600.... or (960/600)^0.5... or Sq Rt of 160%.
 

realdog4

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My first "good" LED flashlight was a Fenix LD20 xr-e q5 back in 2008-2009. I feel like that was around the time when truly led lights were starting to have a major revolution that hasn't really stopped since in my opinion. Now the ~200 lumens that light put out is pretty common even among stuff you can get at stores like Walmart/Target/etc. but it still is an impressive amount of light when you think about it. No consumer products were really doing that outside of much bigger and more expensive lights even a few years before that. Not small single led lights at least that I know of.

So that's a little preface to assure you that pretty much any light you get right now from Fenix, Surefire, Thrunite, Nitecore, Streamlight(sorta), Jetbeam, Olight, and many more are going to knock your socks off if you haven't had a high quality/high powered led light yet from the past few years. Like archimedes said human perception of brightness is definitely logarithmic *with all things being equal*. If you are looking at several lights all in the 600-1000 lumen range (I'm guessing single 18650 lights) then look more at what kind of throw they have, i.e. intensity/candela. Just taking two random lights that I don't even have, but say you have a Fenix TK22 special edition with an xm-l2 putting out 650 lumens (I think that's about right for that light) and a much smaller reflector light with the same emitter (not necessarily same tint) like the Fenix E35 Ultimate Edition (burst of 900+ lumens) or the Thrunite TN12 2014 edition (1000 lumens max). While technically you are putting out more light with those other two lights (which are actually smaller lights) The TK22 with a bigger head and reflector is going to throw more of those 650 lumens farther and collate the beam so that the center hotspot is literally brighter.

I know it's hard to really see the difference if you haven't been able to play around with a lot of lights, but as a lot of people here will tell you including myself I'd rather have a light with fewer lumens that has a super smooth beam with few weird artifacts (the TK22 actually could do that well as it has a micro textured "orange-peel" reflector) and has a great tint (somewhere between 4750-5250 kelvin personally lol) than a light that's just blasting out lumens but has a weird beam with horrible tint and sub-par build and ergonomics.

What lights are you considering right now? Oh and also don't make the mistake of doing what so many people do including myself when I first started getting into lights: Pay more and get good quality stuff from good brands. Seriously stick with the major brands (some of which I listed above) instead of getting cheaper stuff off ebay or other places that may be using the same emitters. You will quickly notice how much build quality and reliability come into play. You really do get what you pay for with high end lights and you won't regret it. The good news is you can get lights that are awesome starting from 30-40 dollars these days from the major brands.

I just bought a Redline rechargeable. It has or claims 300 lumens. I was attracted by the rechargeable factor. It has both a wall charger and one for the car. It was a great alternative to the 6 cell maglite that I owned and wasn't too expensive.

I consider it a good everyday light.

To answer the question which one I am interested in is the Fenix PD35 2014 model. This model, with a battery charger, would maximize my budget.

This seems like a good purchase but if you factor my lack of knowledge with the vast variety of other models, it's far from a no brainer.

I can say that the new redline simply blows away the enormous maglite I own. It was this purchase that made me interested enough to join the forum. I am simply amazed at the difference.

I can't imagine something 2 to 3x brighter not to mention distance.

I am going to have to do some more homework as I am not technically inclined. I have seen technical comparisons with charts and graphs but I really could only grasp bits and pieces. I have more of a linguistic background rather than technical.

Thank you and everyone for their input and responses.

- Jason
 
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ElectronGuru

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I am going to have to do some more homework as I am not technically inclined. I have seen technical comparisons with charts and graphs but I really could only grasp bits and pieces. I have more of linguistic background rather than technical.

There are different scales for different things. The logo scale helps with understanding lumens. But there are also scales for producing lumens themselvs. A challenge with shopping is that each shop uses its own lumen scales. But there are better options.

Each LED family has its own scale. So XPGs tend to be 200-350L and XMLs tend to be 600-1000L. You can generally predict what LED is being used based on which scale a given flashlight falls into. Where a given light falls within a given range, depends on how much power is being delivered to the LED. 3 amps will give more light than 2 amps with the same LED.

Diminishing returns comes within the LED itself. The closer you get to the limits of the LED, the less extra lumens you get from extra power. In practice, changing LEDs works like changing gears in a manual car. The small LED starts less pushed (low RPM) and then more pushed as you near its limit. Changing from small LED to medium is like shifting from 1st to 2nd, when you start again with low RPM as you push up the new scale, escaping the limits of the smaller LED. Escaping the scale of the medium LED requires yet a larger LED (3rd gear).

Continuing the analogy just a bit further, there are also energy and heat costs. Each increase in power, also requires larger batteries to pull from and larger bodies to dump the heat into before hitting runtime and thermal limits of the system they are installed into.
 

martinaee

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There are different scales for different things. The logo scale helps with understanding lumens. But there are also scales for producing lumens themselvs. A challenge with shopping is that each shop uses its own lumen scales. But there are better options.

Each LED family has its own scale. So XPGs tend to be 200-350L and XMLs tend to be 600-1000L. You can generally predict what LED is being used based on which scale a given flashlight falls into. Where a given light falls within a given range, depends on how much power is being delivered to the LED. 3 amps will give more light than 2 amps with the same LED.

Diminishing returns comes within the LED itself. The closer you get to the limits of the LED, the less extra lumens you get from extra power. In practice, changing LEDs works like changing gears in a manual car. The small LED starts less pushed (low RPM) and then more pushed as you near its limit. Changing from small LED to medium is like shifting from 1st to 2nd, when you start again with low RPM as you push up the new scale, escaping the limits of the smaller LED. Escaping the scale of the medium LED requires yet a larger LED (3rd gear).

Continuing the analogy just a bit further, there are also energy and heat costs. Each increase in power, also requires larger batteries to pull from and larger bodies to dump the heat into before hitting runtime and thermal limits of the system they are installed into.

+1 . Something that has been a phenomenon only in the last year or two is super high lumen small 1 18650 lights. These lights are cool, but not when it comes to heat dissipation. Then they are literally not cool. They are putting a lot of strain on a single 18650 to run a light at 800-1000 lumens so they don't last nearly as long as 2-4 cell 18650 lights and also don't usually have as much mass and get hot really fast which requires a thermal step down after a short period of time to a lower output level. If you want a light you can run at really high brightnesses outside you definitely want a 2 or higher 18650 light.

You don't have to go the 18650 battery route though. If you want to stick with AA cell lights you could get something like a Fenix TK41 which uses 8 aa's (get NIMH aa's and a good charger if you do go that route though). That light has great throw and output at 900 lumens or so and much more mAh capacity since it has 8aa's compared to 1 18650.

If you just want a light you can shine around on the high turbo every once in a while though and then are fine with the mid mode (which is still 460 lumens) then the PD35 2014 is a good choice.

There is a currently VERY popular Thrunite TN12 2014 edition which is very similar to the PD35 2014 edition and actually about 20 dollars cheaper. You can get it in a neutral white tint too which I would recommend. Look at neutral white beamshots vs cool white beamshots here on CPF. I don't personally own any Thrunite lights so I can't speak to the build quality. Some have said it's not quite as good as Fenix. I think that's relative though... it's going to be way better than any light you've had probably. If you went that route you could buy a good 18650 battery and a good charger from Thrunite/Fenix for not too much more than just the PD35 2014 by itself. Have fun researching.

I have to warn you though.... once you buy your first good light you quickly start down the road of flashaholicism!!!! :)


EDIT: You reminded me how much I've been wanting a TN12 2014... dang...
 
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NoNotAgain

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+1 . Something that has been a phenomenon only in the last year or two is super high lumen small 1 18650 lights. These lights are cool, but not when it comes to heat dissipation. Then they are literally not cool. They are putting a lot of strain on a single 18650 to run a light at 800-1000 lumens so they don't last nearly as long as 2-4 cell 18650 lights and also don't usually have as much mass and get hot really fast which requires a thermal step down after a short period of time to a lower output level. If you want a light you can run at really high brightnesses outside you definitely want a 2 or higher 18650 light.

You don't have to go the 18650 battery route though. If you want to stick with AA cell lights you could get something like a Fenix TK41 which uses 8 aa's (get NIMH aa's and a good charger if you do go that route though). That light has great throw and output at 900 lumens or so and much more mAh capacity since it has 8aa's compared to 1 18650.
The Fenix TK41 is a great light, whether loaded with rechargables or alkaline batteries. The user interface with two buttons, one for on-off, and the other for power level/mode is about as easy as it gets for a light that produces 800-900 lumens.

I own more lights than I could ever burn up in my life time, yet keep going back to the TK41.
 
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TEEJ

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I'll add that the lumens are only one spec. The cd of the light tells how far the beam can illuminate things at.

So a lot of lumens can be spread out such as from an ordinary light bulb...a 100 watt bulb in a table lamp might be putting out 1800 lumens....but your table lamp would suck at trying to see something 300 meters away.

A light with a tighter beam might be able to light up something 300 m away with only 200 lumens. ..because all 200 might be concentrated on the target.

So, knowing how far you want to see is at least as important as the lumen output.

:)

Generally, if two lights have the same cd, the one with more lumens will have a fatter beam/show more at a time....etc.
 
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martinaee

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The Fenix TK41 is a great light, whether loaded with rechargables or alkaline batteries. The user interface with two buttons, one for on-off, and the other for power level/mode is about as easy as it gets for a light that produces 800-900 lumens.

I own more lights than I could ever burn up in my life time, yet keep going back to the TK41.

Yeah... it's one of the lights that has perpetually been on my want list. Does the newest version have thermal stepdown? I can't remember. I still want to see a TK45 xp-g2 but I'm guessing that's never going to happen lol. Not really any point other than novelty at this point. Maybe if they made it super floody with orange peel reflectors and could get it over 1200 lumens without stepdown? Don't know if 8aa's could even crank enough juice for that though through 3 xp-g2's. I'm guessing they could only do about what has been done with the TK41--- bump it up a 100 lumens or so since the original xm-l version. That would be a pretty cool light though. I remember watching "Prometheus" in theaters and looking around all happy when they used a TK45 lol... nobody else in the theater noticed. :ironic:
 
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GordoJones88

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I just bought a Redline rechargeable.

We like to tease about the Redline brand,
as it is the red-headed stepchild of the family.
Still, a good light is one that you have when you need it.

Don't focus on just the lumens, consider the lux (cd) just as important.
Both of the numbers should be published online for you to see.

If you plan to carry the light clipped to the inside of your front pants pocket,
there are some really small, really bright lights available.

Zebralight SC600 MKII is around 1000 lumens and 10,000 lux (floody)

Eagletac TX25C2 is around 1000 lumens and 20,000 lux (throwy)

Most importantly is a really good battery, or cell.
Eagletac 18650 3400mAh
Nitecore i4 Intellicharger V4

Here is a pic of some of these lights in the Fenix PD35 2014 review :

PD35017.jpg
 
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NoNotAgain

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Yeah... it's one of the lights that has perpetually been on my want list. Does the newest version have thermal stepdown? Maybe if they made it super floody with orange peel reflectors and could get it over 1200 lumens without stepdown? Don't know if 8aa's could even crank enough juice for that though through 3 xp-g2's. I'm guessing they could only do about what has been done with the TK41--- bump it up a 100 lumens or so since the original xm-l version.:ironic:

The TK41 doesn't step-down as the thermal management is pretty good and the head has a large mass to dissipate heat. The biggest issue would be is using alkaline batteries, they'd drain down fairly fast.

Fenix claims almost 3 hours of run-time on Turbo, but I doubt that I would ever use the light in turbo for 3 hours. At that point, I'd use my Surefire Hellfighter and my vehicle battery.

Can't wait to try out my new TM36 to see what run times I can achieve, though it won't be replacing the TK41's in either my car or truck.
 

martinaee

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The TK41 doesn't step-down as the thermal management is pretty good and the head has a large mass to dissipate heat. The biggest issue would be is using alkaline batteries, they'd drain down fairly fast.

Fenix claims almost 3 hours of run-time on Turbo, but I doubt that I would ever use the light in turbo for 3 hours. At that point, I'd use my Surefire Hellfighter and my vehicle battery.

Can't wait to try out my new TM36 to see what run times I can achieve, though it won't be replacing the TK41's in either my car or truck.

LOL I'm assuming you edc that SF Hellfighter? :) And yeah, realdog4, if you do get a good higher end led light that uses aa's get NiMh batteries (eneloops). They work better and won't leak and destroy your expensive toy/tool.

Oh and the redline isn't bad. LOL My cats love my little red Nebo 3aaa light as it has a bleeping laser in the middle of the surrounding 5mm leds. Oh and it has a magnet on the back for some reason. Guess you can stick it on a fridge if you want or on a car or something. Cheaper lights do the same thing all our expensive lights do in a practical sense.
 
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