why increase lumens?

my question is this: regarding a newer, more efficient led, why not increase runtime instead of output? i ask after the 2nd generation of fenix ld12. if you could increase runtime by 20% and leave the output the same, wouldnt that be the prudent course? doesnt a 20% lumen increase only increase percieved output by 5% or so? maybe i dont totally understand the science.

Moved to LED Flashlights - Norm

What to post in the General Flashlight Discussion Sub Fourum.

You are not the only one. I also think that the runtime is more important than more lumens. I'm also looking for Fenix LD41 and the old version have 520 lumen and 2h10min of runtime, the new have 680 lumen and only 1h15min of runtime on max output. This reminds me on phones with bigger screen, higher resolution and more cores in CPU but the battery remains the same. There is no logic.

Every consumer product that is leapt upon by the buying masses , has a tagline like a movie used to sell it :
HiFi had the RMS wars , CPU the Mhz and Ghz , storage MB/GB , broadband Mb (soon to be gigabit) .

I will leave alone the psychological implications and my personal opinions out of this post

Mervmaster said:

my question is this: regarding a newer, more efficient led, why not increase runtime instead of output? ...

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They can... and they do... but the bottom line is that lumen specs sells... not runtime. Take the ET D25A XML2 for example - 141 lumens for 1.3 hrs that's 183 lumen-hrs. Now take the ZL SC52, it's 280 lumens adjusted to a [more conservative/less exaggerated?] ET scale is about 225 lumens and Selfbuilt ran it to 50% in 0.8 hrs - that also about 180 lumen-hours.

So how many times have we read "the SC52 can do 280 lumens on an Eneloop" vs "the D25A can do 1.3 hrs on max?" ;-)

(BTW, I have both lights and a Quark AAX, and have tested them side-by-side with a light meter and stopwatch... I find them far more similar - neck and neck really - on lumen-hour basis than a comparison of their spec sheets might suggest - I personally believe the ET/47 lumen scale, time clock and printed ink to be far more accurate, YMMV).

I am not bothered about run times,makes no odds to me if it runs for an hour or 2 hours,i just stick another battery in.I invested money in the lights so why should i be a skin flint on not wanting to pop another Eneloop in.

Power sells not run times which has already been said.

There will always be a quest for higher lumens. I prefer the higher lumens, and the theory of only 20% can't be perceived is individual perception. If you think about it what if it was increased 20% 5 times from the original, then would you say you can't see the difference.

Mervmaster said:

my question is this: regarding a newer, more efficient led, why not increase runtime instead of output? i ask after the 2nd generation of fenix ld12. if you could increase runtime by 20% and leave the output the same, wouldnt that be the prudent course? doesnt a 20% lumen increase only increase percieved output by 5% or so? maybe i dont totally understand the science.

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Why Increase Lumens?

Fortunately, some lights have selectable levels so that you can choose your lumens. Less lumens equals longer run time.

Re: Why Increase Lumens?

I wouldn't even consider a light that has high lumens output, short runtime, and no lower-output mode(s).

On/off is acceptable if lumens output is enough (to perform job that light is typically used for), but chosen such that it has good runtime too. A 'sweet spot' in the output vs. runtime curve, that is. Much lower than that and it'll run long but be useless, much higher than that and it will light things up but for too short a time (either of those cases = job not done in my book :scowl: ).

When the light does have several modes (and they're spaced reasonably), then the above isn't relevant and yes, why not include a max output level to impress people? (or myself).

FWIW: given battery limitations, usually the lower modes are more useful anyway IMHO.

FlashKat said:

There will always be a quest for higher lumens. I prefer the higher lumens, and the theory of only 20% can't be perceived is individual perception.

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No, it's not individual. To tell that low of a difference, you will need to compare to light sources offering similar lux throughout the beam, at a similar CCT, and then it's still not going to be easy.

If you think about it what if it was increased 20% 5 times from the original, then would you say you can't see the difference

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20% is quite far from 149%. There's also no reason to not increase the maximum output when it becomes noticeable, except to save pennies (I have a hard time imaging it's too much, for any mass produced flashlight, for what is likely nothing but changing resistor values, or a table in the firmware).

Either way, IMO, increasing the lower output modes is not merely wasteful, but reduces the utility of the torch. FI, after those 5 generations, a 10lm low would become a 25lm low. At that point, it might as well not have a low mode, anymore. The same goes for a 50lm medium becoming 100+lm.

I am not talking about increasing the low lumens. I assume you don't own any lights over 100 lumens!!! I sure hope not since it is a waste of lumens.
I have several lights that are high lumen with very low lumen settings. I prefer to have high lumens for the times I need to see far, or just see well.

cerbie said:

No, it's not individual. To tell that low of a difference, you will need to compare to light sources offering similar lux throughout the beam, at a similar CCT, and then it's still not going to be easy.
20% is quite far from 149%. There's also no reason to not increase the maximum output when it becomes noticeable, except to save pennies (I have a hard time imaging it's too much, for any mass produced flashlight, for what is likely nothing but changing resistor values, or a table in the firmware).

Either way, IMO, increasing the lower output modes is not merely wasteful, but reduces the utility of the torch. FI, after those 5 generations, a 10lm low would become a 25lm low. At that point, it might as well not have a low mode, anymore. The same goes for a 50lm medium becoming 100+lm.

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While I do agree with the lumens quest argument I would also throw out that there is a cost of RnD and manufacture. When a new LED version comes out with more lumens I imagine it it much easier to just start making the light with the same driver and just put the new LED into the production line. If companies designed a new driver to keep lumens the same it would take time and cost more money = less profit.

Best bet is a multi level light if your buying from the mainstream market. If you are buying a light with a custom programmable driver then you can drop the current to keep the same lumens and benefit in that regard.

Now THAT is probably exactly correct. Easier to change your packaging than your production line I suppose. But I wonder if they don't change the circuitry. Not even a little? Is a new led enough to just drop in and get a lumen bump without changing the driver at all? Especially if you need to keep your advertised runtimes. Maybe within the same led family.

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reppans said:

...the bottom line is that lumen specs sells... not runtime.

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That's the entire debate in a nutshell. Tell the average Joe how much, say, an HDS Rotary costs, and his first question will inevitably be, "How bright is it?"

FlashKat said:

I am not talking about increasing the low lumens. I assume you don't own any lights over 100 lumens!!! I sure hope not since it is a waste of lumens.
I have several lights that are high lumen with very low lumen settings. I prefer to have high lumens for the times I need to see far, or just see well.

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Again with the derailments. Whether low lumens or not, 20 != 149. Usually, it is a waste of lumens, though, hence having multiple output modes on anything that bright or brighter. But, even then, if 120lm does the job, 150lm won't do it any better. If 500lm does the job, 625lm won't do it any better. And so on. If 120lm will not do the job, though, 299lm might. If 500lm will not, 1240lm might. 20% 5 times is a huge difference, compared to 20% once...but, not always in a good way, as 1240lm might be too bright, when 500lm would do, and you still use up the batteries just as fast.

It's generally going to be a matter of changing a resistor or two, to change what the modes output by the light, if any changes need to be made physically (a PWM light shouldn't need anything but some firmware values changed). If you have a 50lm setting on gen 1, and gen 2 that goes to 60lm, you have lost potential battery life, yet gained nothing in utility. If it increases to the point that you end up with no mode near 50lm, it's not only gained the user nothing, but actually reduced the utility, compared to a prior version. You'd be better served by the sense resistor, duty cycle settings, or however it's done, changed to make it 50lm, and gain nearly 20% more runtime. I'm quite sure it's simply not done for ease of manufacture, and due to not planning for future LEDs on the same driver. If the driver is planned out with new LEDs in mind, then they could keep most of the modes the same, and only increase the maximum, until such time that the maximum becomes too far spread out from other levels (by then, chances are they'll have a new body generation, too, if not a whole new model designation).

When we have 5000 lumen mules that are the size of the Malkoff Wildcat and never have thermal issues, we can worry about runtime.

I have never met a flashlight that was too bright for my needs. Now if a bird accidently flys into the beam and disappears in a cloud of stinky smoke that might be a sign we are getting close to enough candlepower.

I don't mean to imply that lights are getting too bright- just the opposite. I see huge lumens and I'm sucked right in. I just think that if its only a 20% bump I'd prefer longevity to a minor brightness increase. Just my opinion though. Live long and flashlight.

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With rechargeable batteries easily available, run time is not an issue. Just put in another battery or recharge it.

twl said:

With rechargeable batteries easily available, run time is not an issue. Just put in another battery or recharge it.
In nearly 60 years of using flashlights, I have never ever run any battery flat in my flashlight, ever.
In real life, it just doesn't happen. In people's imaginations where they think they will be stuck in a cave for the rest of eternity and only have one AAA battery to last them forever, then it matters.
In real life, run time is completely irrelevant. That's why they make batteries and chargers.

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I wouldn't say runtime is irrelevant. It's easy to say that you can just recharge batteries. But there are going to be those times where doing so isn't convenient or even possible (solar chargers are helpful in the middle of nowhere, but they can't charge at night). Good examples of this are camping, hiking, and (as you pointed out) caving. It's always possible to take more batteries. But it may not be desirable from a size/weight standpoint. Also, changing batteries in pitch darkness can be just plain inconvenient, eapecially on lights using battery carriers. In these sorts of situations, runtime is ANYTHING but irrelevant.