Lumen and lux measurements, why cant we all try to be on the same page?

Im not seeking perfection. I would just like to see that the gaps between people that seems to consistently be around 15-20% off. Based on posts by Tom E, im quite sure he have noticed this and is aware of the "issue". Its not hard to notice that certain guys are consistently much higher than others.

I can easily measure a light just based on ceiling bounce, and then easily choose if I want to be similar to the high lumen guys or the "ANSI lumen guys" despite all the variables. These days, I currently somewhere in between. Although if we could all meet with the "ANSI guys" that would be better for everyone IMO.

Most of the ANSI lumen guys are very close to each other. And then there is a gap to others.

For people who dont have a lot of comparison lights, premium lights, etc to use as reference, it may not be that easy to get a good calibration. Im certainly not claiming that. But even at my level (no integrating sphere), I easily notice the differences in both lux and lumen numbers. For the people who share numbers all the time, have measured xxx amount of various ANSI rated lights etc, it seems fairly easy to get closer to other..

I do not remember publishing any lumen values in my reviews. I have never had anything that I trust for precise lumen values. The "Estimated lumen" is not a measured value, but as it says an estimated value and it is based on the specified maximum lumens.

I know that in some of my comparison the scale looks like lumen, but I do never say it is lumen.

is there a cheap and easy to do possibility to get 2 fixed amounts of Lumens to “calibrate” our meters within some percent?

First point is to get a lumen meter, it is not cheap.

All the home made integrating devices might work more or probably less well. To test it: Try aiming the light in different directions into it, the lumen reading must be stable if it is a truly integrating device.

I have read and read over and over about this, on CPF and here. There's much better info over there. Basically, you will never be "within 15%-20%" with a home setup. The only true numbers will cost thousands of dollars. You can use home systems for "guesstimating" only and since there is no standard for these home systems, then there is no way to control the numbers, or the fact that they are all so far off from each other. The only way to find anything out would be to:

Go to a company that has the high priced system and have certain lights tested. Take your sphere with you to test your setup against theirs and make calculation adjustments to your readings, to get close to theirs.

Then send out those exact lights and exact batteries to others and have them do the same thing with their systems, till you had a base of a few people that were getting the same results consistently. Then it all has to be rechecked and verified once again every time you use the system, before trying a new light in it.

Not feasible and that is why I did not try to make a sphere. Even if you could make one that was close, it would cost thousands of dollars to buy a bunch of lights that have been ANSI qualified and it still wouldn't help, since you don't know what they used to power them at the time of testing, or the conditions of the tests. I don't listen to any of the numbers I see around here, because no one here has the correct setup to accurately test. They never will. If you really want good numbers, then you would have to buy a real integrating sphere and the software and accessories to do correct testing. before I ever believed any of the results. What we do around here is total guesswork and it's never really going to be accurate, no matter how much some people "believe" they are doing it right. Saying joe should cut his results by 15%, or john should do this, because he has xxx meter is just more total guess work and does not help solve the problems.

No one should be publishing their lux/lumens readings from any home meters or spheres, because there is no assurance at all, that they are even close to correct, so it's not good to even post them. Same for throw numbers. It's misleading for others. I don't mean that people are doing wrong on purpose, but it's still wrong. Unless it's lab checked and verified numbers, it's not relevant information. Better off just guesstimating from amps, if true amp readings can be gotten. Mine sure aren't.

Just me spouting off, I do a lot of it any more.

Was I was asking for is a “thing” that emits exact known Lumens…

by comparison it should be possible to get good numbers even on a cheap meter…

Lumen is difficult to measure, but lux is not nearly as difficult.

The main problem with lux is filtering: Lux is defined to follow the eyes sensitivity to colors, a silicium sensors does not have the same color sensitivity. This can be fixed with filtering, but good filters cost money, another way to fix it is with different calibrations, depending on light source, i.e. a meter that can be switched between different light sources does not have filtering, but only calibration for the light sources.

A meter like this is fairly good for lux:

any flashlight with ANSI rating

ANSI ratings mean absolutely nothing… just like UL/CSA/VDE labels. They are only as good as the paper they are printed on. Anybody can say their product is ANSI/UL/etc tested. Whether or not it actually is is pretty much a matter of trust. Even checking UL file numbers… those can be copied even easier than the product being counterfeited.

As far as lumen numbers are concerned… unless you have a decent sphere they mean absolutely nothing. Integrating ceilings, bathrooms, boxes, pluming pipes, eyeballs, or squirrel butts, etc are useless and misleading.

Lux numbers are a bit better… but I have seen cheap lux meters from the same maker, shipped at the same time, disagree by 30%.

Good thread. Good idea to have a standard BLF approach that members can try to implement, but not be beaten up for when they don't.

I've never tried to measure lumens as I don't even know where to start with a ceiling bounce (e.g. how far from ceiling with light, then with meter, what color and sheen paint on ceiling to use, popcorn or flat ceiling, etc, etc.).

For throw, I think it is good for folks to include the distance they took the measurement. I try to do that, but I haven't identified the meter in my reports.

For stock K50 V2, I measured 198kcd with the ubiquitous HS1010A (I think that's the model number).

No, manufacturers openly admit you will see +/- 7% from one exactly the same light to the next, in reality 10% difference isnt uncommon. You can buy a calibrated reference light (or build one and have it professionally certified at a lab) but an off the shelf flashlight, even from top tier manufacturers, is NOT ” a thing that emits exact known lumens”.

I think about this things often and came to no solution because like others said there are to many different variables.

I once hoped we would all “calibrate” our meters to the olight i6 which everyone bought and which seemed to have a output which is not sensitive to the used batteries…but it never happend.

A funny option would be constant current light which we would pass around and everyone can measure its lumen and lux. Maybe a man in the middle which gets submitted all the data and once everyone has it had it gets published. That would be fun to compare and I am sure we would see huge differences like racer said.

Another funny option would be a cardbox “integrating sphere” produced in china and send all over the world so that everyone has about the same…

An idea I have had for a while, inspired by a suggestion never carried out by match:

I am going to build a simple 18650 flashlight one of these days, lowly driven by a lineair driver (I have done this before, the output will be very constant and virtually independant of battery type or state) , then measure lux@1meter with my luxmeter and measure it in my integrating sphere and produce some djozz-lumens ;-) . Then I am happy to send it on a roundtrip around the world to other BLF-members, and have them measure their DBC-lumens, TomE-lumens or whoever is interested. And finally I receive it back and see if it still reads the same.

Using one and the same flashlight will at least reduce the number of variables (it will certainly not solve the problems related to the bad colour filters on the sensors of cheap luxmeters), but beside that I think it is a very fun thing to do :-)

You just beat me there posting about the pass-around flashlight, Werner :-)

I hope no one reading my posted measurements consider them the golden standard, or think I have some magical home setup that has a 0.0001% tolerance. NIST comes to me btw to calibrate their test equipment Smile.

What I don't like is the cherry picking of my posted #'s and emphasizing like it's typical. I can't explain all the differences, but many lights I've measured dead-on to manu specs or within an acceptable tolerance (maybe 3% is acceptable?), others lower, others higher. Sometimes I know I see variation in the positioning of the flashlight head on the glass of the PVC lightbox but I use it as precisely the same as possible, and I can't notice a consistent pattern that high throwers, high flooders, low lumens, or hi lumens get higher/lower readings. Do I or did I screw up sometimes? Sure I did - no doubt.

I do believe (from real, actual direct comparative measurements) that my $35 meter is accurate enough and compared very well to a much more expensive ExTech meter. In fact two of the $35 meters matched up well to an ExTech meter.

Also I have no idea where the notion or inference came from that we did not use ANSI rated lights to do the initial calibrations. Of course a multitude of ANSI rated lights were used. In fact there were probably at least as much or more ANSI rated lights used in the calibration process than others making the claim. Did every PVC based lightbox/meter combo get the same level of testing? - No. One setup was tested more extensively, others were built in the same design, then lights were shared, measured, compared, and calibration factors derived as a result.

However many ANSI lights are/were used by anyone, though, is not enough. There's too many variations from piece to piece, LED to LED, reflector to reflector, etc. in the so-called ANSI lights, noted and documented by many, like vinh and Michael at OSTS.

Now let's take a look at conservative/aggressive approach to this measurement dilemna. I believe my approach was conservative to the calibration, then aggressive to the measurements. Out of my collection of hot cells, I'll post the #'s on the cell that gave me the highest readings. How does this compare to the so-called ANSI lights? Well all depends on the approach the manufacturer, or contractor/facility the manufacturer hires to do the measurements. In theory there should be only one measurement - the accurate one, but that seems hard to obtain with almost any equipment. I think some manufacturers tend to take a conservative approach, fearing they will get in trouble by over-stating their "ANSI" claims, while under-stating is far less risk.

Passing one light around the world will help, but you really need a few representing different sizes and designs.

Here's a good example of readings I took on the NiWalker MM15, stock, on May 22nd:

MM15 clearly states "FL1 STANDARD" on their published #'s:

NiWalker my lightbox/meter (all in lumens done at 30 secs)

Mode 1: 6 11

Mode 2: 180 167

Mode 3: 450 483

Mode 4: 880 874

Mode 5: 1950 2013

Mode 6: 5233 5236

Throw: 19.6 kcd 17.2 kcd (measured at 5m)

Now I consider these dang close. Some might say mode 1 is way too far off, and it certainly is in percentage, but, you have to consider this is a high powered light using two MT-G2's. When these two LED's are cranked down that low, system tolerances andd variations are going to have a bigger effect, so this is not surprising to me.

In fairness, for Mode 6, I had 3 #'s written down, but this one was marked "cool", meaning the light was off long enough for temp. not to be a factor. The other readings wee 5,059 and 5,202.

Do we trust NiWalker enough to ensure they followed the ANSI FL1 standards to the letter when doing these tests? Me? No freak'n way... I don't trust any of them, be it Olight, Klarus, whomever. I know way too much about what goes on (or what doesn't).

Ohh - btw, what if NiWalker can't get P0 bin LED's, but found a source of Q0's, so they do their next batch run with Q0's. Do they re-test under the FL1 standard for the new batch run at a cost of $1,000's, maybe more? Do they update the shipping boxes with the new specs, and throw out the current inventory? Or maybe it's just for one batch, so do they pay for a special run of the shipping boxes, probably at another insane cost for a low volume? Oh sure they do - they only think of the customer, I'm sure... Smile

I recently purchased an HS1010A. I haven’t started any output tests but have completed throw numbers for all my lights.

I practiced for a while until I found I could get repeated, consistent results.

I had a few lights (Jacob A60 and two T08s) that I measured before and after mods. The mods I did on all three lights were pretty much standard affair, higher amp drivers, de-domed emitters, copper, resistance mods, etc.

I was surprised when I started comparing my numbers to similarly modded lights by others. With all 3 lights I found my stock numbers were a bit higher and modded numbers were significantly lower.

I did not expect in any way to be matching the kind of throw attained by some of the folks here but thought I would at least be in the ballpark.

I’ve decided as long as I can produce consistent results I can use my numbers to quantify my mods. That’s really all I wanted to do with the meter in the first place.

It might be agreed that Texas Pyro has some of the best testing equipment amongst us. Perhaps he will agree to test a light, any light, and see how it compares to the testing we do at home? I don’t have fancy computer print-outs, and yes, sometimes I can barely read my own notes even if I can reliably find them.

But wouldn’t it be interesting to pick out, say, the SupFire M6, charge up the cells and run my tests then charge the cells back up and send it to TP for his run and see how the 2 compare? TP would then argue that his expensive equipment was right, however the numbers fell. :wink:

For me, the lightbox tells me what the light is doing when I get it, and then how much difference my mods made. If the difference is not what I expected, I then check ground and other issues and test again, sometimes then finding the expected results, sometimes not. But it’s a guideline, for me, right here, doing the work and then confirming or busting whether the work was worthwhile.

Yes, I use a LX1330B. You will probably find that myself, rdrfronty, Tom E and Richard all have similar results from lights, because we’re all using the same meter and same base system. rdrfronty and manxbuggy1 spent many hours, days, weeks even, testing as many verified lights as they could get their hands on. (and their hands hold a LOT of lights!) My own box was verified against theirs, and with 20 or more of their own verified lights. So I feel confident that the results are accurate enough for me to base my builds on.

I don’t think any of us has ever said “THESE ARE ABSOLUTE NUMBERS!” Because we know the variables are everywhere. I can almost guarantee that you get a major factory to test a light, chart the numbers then send it to me, and after I test it and write everything down, send it right back to em for a second round and their own numbers will not match the first run. It’s just the way these typically work. The LED get’s burned in, the cells get some age on em, the driver has it’s own quirks and oddities as it’s components get hot and cool down. And such is the way of life.

Maybe I can build one of the Eagle Eye X6 lights and test it, then send it around to everyone else that has a box and we can average all the numbers, compare notes, and adjust our multipliers accordingly so we can all be on the same mystical page….

A VERY interesting thread as I have just had RMM modify a group of lights for me and I asked to receive his sphere results for all of the lights he did for ALL levels, not just maximum. Some of the max readings were higher than I expected and some lower but at least I now have a record of what the lights were calculated to be putting out based on Richard’s equipment and measuring technique.

From our email exchanges I got the impression that Richard uses his sphere the same way that Dale says in his post, as a reference for checking that his light modifications are putting out what he expects based on experience. Is it dead on to ANSI, almost certainly not. Is it in the same ballpark? I hope so. Just based on Cree binning specification limits I would expect ANSI spec lights to give different results for different individual lights even in a certified lab with NIST calibrated equipment.

A max modded SRK soup can triple and a max modded M6 were very close which I would expect with the same LEDs and batteries in both and basically direct drive on maximum output. Both within 1% and about 4600 Lumens. I have seen similar readings for a heavily modded M6 from another source. The champion he did for me though is a Supfire L1 which gave a reading of 7000+ lumens max and it now has the latest 7 levels RMM offered firmware in it with “hold for off” from all output levels. Even if optimistic that is one hot light and with a MUCH better UI IMO than the original.

Added:

All the tests RMM did on my lights were done with Sony VTC4 unprotected batteries which are high current low internal resistance batteries. Per my understanding the use of these or similar high current low resistance batteries can substantially increase the output of direct drive in highest mode lights such as most soup can lights are.

I had some conversarions by email with a very friendly guy from a light testing company about how flashaholics measure their output. He was quite impressed by the level of knowledge there is around here, and the testing equipment we make, but 1) he warned about the bad colour filters of cheap luxmeters, giving inaccuracy for different wavelengths, and 2) he could not find out how on earth we dare to use the word 'lumen' without going to a test facility to calibrate the equipment (this was not because he would make money from that), I guess he was not at all impressed by the accuracy of ANSI-numbers going with flashlights.