What qualifies as a primary light?

[Duglum]

1500 is the lumen rating. Lux is the lux rating. Is that tricky?

No, but either that is not true or the table you posted doesn't make any sense. When the battery used and the Lumen Output are constant, the only way to change the lux is to narrow down or widen the beam. Which doesn't influence burn time. At. All.

 

[eelnoraa]

Following what TBONE and Stuardv said.

I think T explained it very well already, and he is using a very optimistic assumption in his example. At high current mode, say 2-3A of current drawn, the overall efficiency of the system is not even close to 95%. It is more likely on 80% range. The single cell itself will lose 10% to heat at such high current mode. The interconnect metal lost will play a role. The driver efficiency will pay a role.

In reality, LiCoMn cell is about 4500mAh these days. To get 4 hour constant runtime, the current drawn from battery is about 1.1A. With this current dawn, maybe 95% efficienty is possible, so LED receives 1.05A. If LED is XML2, 1.05A will give you just below 500 lumen. You can get 1 hour of runtime for about 1000lumen. Just Sturartv pointed out, even 900lumen at 4 hour isn't possible with 1 26650. Now you can probably use a more expansive LED to get more luman per watt, but maybe 10% more is what you will get, not 300% more at 1.1A

The more I do math, the more I think this TillTec isn't any better than Chinese lumen by much.

 

[stuartv]

I believe "LED 1500" is the product name and the lux ratings are for three different brightness settings. Tilly has a history of really confusing product names and descriptions...

Aha. I get it. So, on high, a burn time of 1.5 hrs.

So, the statement earlier about 1500 lumens and 30000 lux for 4 hours from 1 x 26650 battery was misleading to the point of considering it to be totally wrong. You don't get 1500 lumens for 4 hours. You get a light that is rated for a max of 1500 lumens, but is on Low, so it's actually putting out half its rated max (which was stated to be 60000 lux on High, apparently), for 4 hours. That is totally believable - just not what any normal person would interpret as what he said earlier.

EDIT: I should own more of this. The original post did not say 1500 lumens. It only said a lux rating. I just assumed that 1500 was given as the lumen output. That is my bad.

Bottom line: On High, the specs say the light runs 1.5 hours on 1 x 26650 and it will run 4 hours on Low. Totally believable (as a possibility), given that we don't know what LED emitter(s) is being used or how many lumens it's putting out.

I think my Xtar D26 will also run 4 hours on Low, with 1 x 26650, no problem. The real question is, so what? I don't think anyone here was really talking about burn times of lights when they are running on Low.

 

[eelnoraa]

So Lux and lumen are very interesting thing. Lumen is measured of total amount of light. We perceive this as how "big" the light is. Higher lumen light up a bigger room but not necessary brighter room. So I don't agree with Halcyon's statement about you can't measure lumen. You can definitely feel more lumen is there because it lights up bigger area. You can get high lumen in 2 ways:

1) lot of low lumen light source. Each time you add a light source, the lumen adds. That is why Solar light can get to high lumen value. This type of lumen usually has low lux because lux don't add. Solar light is a perfect example here. They don't produce a very intense light , but they light up a larger area. This kind of lumen is easy to get to because LED is more efficient at low current drawn.

2) one high lumen light source. This type of lumen, you can get your high lux if focus properly. The best example here is HID light.

Lux is measure of intensity, the brightness we perceive. For a given LED, you can focus it better to get higher lux, but there is so much you can do. After that, the only way to increase lux is to have brighter (higher power) LED. So in a sense, high lux will require high power source (high lumen unit source). High lumen can be archieve with increase number of source. To get both high lux and high lumen, you need to start with high power LED, add LEDs to get to the lumens.

 

[eelnoraa]

Well email or call Thomas Tilly and ask him is all I can say. I'm not selling anything and have no commercial interest in this. I have both the older 1500 and 900 lights and they fall within the industry agree definition of burn time he claims. I therefore have no reason to disbelieve him. Kind of GM vs VW....

We are just trying to tell you that with today's known tech, the combination of run time, lumen, they claim on their website is NOT possible.

 

[Aotus]

"run time" and "lumens" are often reported, and may be true, that's not what should be debated because the claims can be true AND false, ultimately depending on when you test it. The factor that Tbone and some others (like me) have brought up here is that lumens can drop off so that you get both the claimed lumen output (for a minute) AND miraculously long run times. I cited the website www.wetestlights.com before, and to reiterate the point about change in lumens with time, I will post the graph from their comparison page. Note that at different points you can say that either has the brighter light. You'll also note that neither of the lights were able to live up to their claims.

1. Hollis light LED 25
claimed lumens: 1250, measured max lumens: 587
claimed run time: 480 minutes, measured run time: 377

2. Light Monkey 12W LED
claimed lumens: 750, measured max lumens: 457
claimed run time: 300 minutes, measured run time: 422

For good measure, here is a pair of Big Blue lights that illustrates one way that they are able to live up to their burn time claims.

 

[victorzamora]

4 hours at 900 lumen on a single 26650 is beyond our current technology. Do not believe those claims. Let's give 26650's a bit of an improvement and say they are 6ah, which is well beyond what they are, but it makes for easier math. Cree XML's have a max efficiency of 170 lumen/watt, which they don't get, but it's a number. 3.7v*6ah=22wh for the battery. 4 hours assuming 100% efficiency and full use of the battery is 5.5w draw. 5.5 watts at 170 lumen=935. That is before any efficiency adjustment *at best 95%*, that is assuming a battery that has a much larger capacity than it really does *they are usually at 5200-5300mah, and assuming they are getting the best efficiency out of that emitter, which they aren't. This light is beyond both the LED technology and the battery technology we have today, don't buy into marketing claims.

For note: These are some extremely generous numbers tbone is providing. 170lm/W max is in a very specific band, with an incredible driver, lots of luck, and no loss of light through the glass or reflector. 110lm/W is much closer to accurate, and even that is quite generous.

 

[eelnoraa]

another issue with LED manufacture is the model number. Hollis claims their LED25 is equivalent to a 25W holegen? or 12W halogen in LM's case? First, I think this kind of naming convention is ridiculous, so misleading.

I have owned LED25 at a point. The consumption from battery terminal is about 10W. let's assume efficiencty of 80%. 8W goes into the LED. I would expect a ~800 lumen light output. Which is somewhat align with my measurement/estimation. My number is more of 900-1000lumen. I wonder what is wetestlight's measurement method is. It it is similar to mine, the number can be under estimated. But here is how I did mine

Lumen is very difficult to measure if possible at all. At work,, I have very accurate measurement instrument for current flow, lux, and thermal imaging. The camera for lux measurement has an sensor that does NOT do weighted average of the capturing screen (of weight is 1 for every pixel in the sensory). To estimate the total light output, I shine the light close enough to a white wall (usually 1 meter, but sometime it needs to be much close), then back up the camera enough to cover most of the lighted area. Then I integrate the lux reading with the area to get the total volume of light. This number should be directly related to lumen number. To translate this number to lumen, I normalized this number with a known LED (XML2-U2) in my case, driven at a known current ( 700mA in this case). If the target light also use a XML2 LED, I again reference the reading to the data sheet. This method has been consistent for the lights have tested, so it should be somehow accurate.

There is one big limitation here. It is my lux sensor can never backup enough to cover the entire lighted area. The more define the beam it is, the less uncovered area. Beam with more diffused halo, such as HID, this method will under estimate the lumen value. Since I can't quatify how much the underestimate is, I don't account for this. But it is safe to say, for the useful beam area, I should have it covered.

With this method, I have debunk so many inflacted lumen output. The only high lumen LED measure up to the claim is LD2600 so far I borrow from a fellow diver. It meas-estimate~2400 or so with my method. But LD's beam is also very diffused, so I am not surprised at all that 10% of it was not covered by the sensor.

If I can get a Tillytec in my hand. I am happy to do the measurement to compare to its claim.

A few things I learned:
1. It is unlikely human can feel the difference between say 800 and a 1000 lumen. The number needs to change big to be noticeably (50% at least).
2. In terms of usefulness, lumen matters more than lux. With increase in lumen, you feel more of the room is lighted brighter. With increase in lux, your eyes feel more strengthed looking at the high lux center, the rest of the room is still dark.
3. 1000 true lumen is a lot of light, more than most people need under water. In fact, 300 true lumen is a lot of light already. It should be good for most non-video diver. So forget about those 15K lumen light if you are doing AOW night dive. Get a honest 300 lumen light.
3. Under water, lux punches in murky water. Lumen light up more water.

 

[Aotus]

I wonder what is wetestlight's measurement method is...Lumen is very difficult to measure if possible at all....

Lumens can be measured. At Light & Motion they use an integrating sphere, and they apply the ANSI FL-1 standard for testing (standards). According to their website (www.wetestlights.com), they started sharing results of their own tests of other brands because they were tired of reading inflated bogus claims from their competition.

here's a video from a different company explaining the integrating sphere for testing lumen output over time and why lumens are useful and lux is not:

FYI: I am not involved with Light & Motion, I don't even have one of their lights. But in shopping around and speaking to a number of companies about their lights recently, I have been SUPER impressed with L&M and they're really opened my eyes to the nature of the light business. I used to think they were all hype and overpriced, but now I understand they they one of very few companies that sells what they advertise.

 

[bamafan]

I am sure the Becky Kagan's of the world with their super high end cameras can probably tell a difference in the difference between the high end lights and the Big Blue lights but for the majority of the divers out there they will never notice it. I did a couple of cave dives in Cozumel over Labor Day and after 1.5 hours the Big Blue 30k lumen video light was still way brighter than my 6k lumen UWLD video light. For about $1k for the Big Blue video light I personally don't see why most people would spend the extra money.