Does Double the light equal double the power?

As I am a noobie to this, I apologize upfront if the title of this thread is not as clear as it could be.

What I'm basically inquiring is: If I hold my Jetbeam RRT-3 and shine it in my backyard on turbo mode, I'm getting 1900 lumens. If I then take my Fenix TK 35 and shine that on high, which I believe is, let's say, 800 lumens, am I now putting 2700 lumens down on the ground? It doesn't seem so.

It's obvious to even a dummy like me that it's not going to make the throw longer, but it also doesn't seem like the area is that much brighter, as it would be, at least I think it would, if I were shining a 2700 lumen light alone.

Can someone please explain this to me, but in simple terms. I'm sorry that I'm not able to understand difficult math equations.

Thank you.

Mark

The lumen rating is the total amount of light coming out of the emitter, it's not the amount of light being placed on a specific area; since that light can be distributed any way, specifically a floody or thrower light, one light may put more lumens into the spill, another light may have a large hotspot, etc. You are emitting a total of 2700 lumens, just not in one confined area.

Also, you perceive differences in light levels by large leaps in percentages; you don't notice a difference at all until at least a roughly 10% change. Your combined light output is only about 40% over the Jetbeam's output, which you would perceive as modestly brighter at best.

Play with candles. The Jetbeam is 2 candles, the TK35 is 1. Put a table against the wall, stand a book up sticking out from the wall. Light 2 candles on one side and one candle on the other. Both sides of the book look well-lit, but where the light of all 3 reaches it doesn't look very much brighter. Where all 3 shine, it is 3x brighter than where one shines, and 50% brighter than where only 2 candles shine - you have 3 candles instead of 2. A good rule of thumb is that it is pretty hard to notice a 40% increase in light concentration.

Light concentration measures how much light there is per area. 3 candles is 3 times as many lumens as one. 'Lux' is lumens per square meter, or light concentration. The candle experiment compares 1x to 2x to 3x lux, and shows that even tripling light output isn't that dramatic.


The way the human eye works, you perceive light 'logarithmically.' That means that it takes a pretty big step up in light to look noticeably brighter. That is what you are noticing.

I mentioned 'light concentration,' lux, above. Flashlight output patterns are sometimes made to produce concentrated light, or a high lux value. This is great for seeing distant things, but not helpful for working up close. A bare lightbulb is all spread, and a focused searchlight will reach farther. Some people confuse higher lux with higher output.

A good example of this is my Zebralight (headlamp). The step up in brightness from one mode to another is roughly 300% each step up. Any less and it's not all that noticeable or at least substantial.

The lumen levels are 2.5, 7, 30, 100 and then 200. The increase from 100 to 200 isn't all that impressive. The other increases 2.5-7-30 are all very noticeable and useful IMO. So to me a 3x step up or down is optimal.

I think the human perception of an increase in lumen is comparable to how the unit decibel (dB) used to measure sound works. An example: One Zebralight SC51 on high puts out 200 lumen. 10 ZL SC51 on high side by side put out 2000 lumen, but it doesn't seem to the human eye like they are 10 times brighter. If one guy playing the trumpet "puts out" 100 dB, 10 guys side by side DO NOT put out 1000 dB, which would kill you. My theory is that dB is a truly logarithmic unit, whereas lumen is not though it is perceived, as AnAppleSnail said, "logarithmically".

I hope I made some sense

Swede74 said:

I think the human perception of an increase in lumen is comparable to how the unit decibel (dB) used to measure sound works.

Click to expand...

I understand what you're saying and I agree with you, but your analogy makes the subject confusing (nothing I haven't done before myself ) because dB is logarithmic while lumens is linear, but they're both units that measure output, in a sense, and there is a great temptation, I think, for people to compare them directly, which should not be done.

Swede74 said:

An example: One Zebralight SC51 on high puts out 200 lumen. 10 ZL SC51 on high side by side put out 2000 lumen, but it doesn't seem to the human eye like they are 10 times brighter.

Click to expand...

Right, in this case the units are linear while the perception is roughly logarithmic.

Swede74 said:

If one guy playing the trumpet "puts out" 100 dB, 10 guys side by side DO NOT put out 1000 dB, which would kill you. My theory is that dB is a truly logarithmic unit,

Click to expand...

dB is definitely logarithmic, so your theory is correct. Sound adds together much like light does, but you can't simply add their dB because the unit is logarithmic--you'd have to convert to linear units in order to add them, and then convert back to dB. It's a mathematical issue, not a physical one.

Swede74 said:

whereas lumen is not though it is perceived, as AnAppleSnail said, "logarithmically".

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Lumens are linear, which as you said does not match perception. I suppose that a logarithmic measure of light could be made in order to better match perception, but that's not how things are currently.

Swede74 said:

I hope I made some sense

Click to expand...

You made perfect sense, but I hope that it didn't confuse those who are not as familiar with these things. I don't know, maybe I just confused them more! :shakehead

Suffice to say that lumens do add up, they represent total output but not necessarily all aspects of perceived brightness, and that perception is not on the same type of scale (generally the brighter the lights, the harder it is for us to tell the difference between them).

I very much appreciate the responses and actually understand it better now.

Now to await delivery of my tiny monster which I got with Amex points, so sorta free. This is a fun hobby.

Mark

Did you mean to type 100 percent instead of 10? If not I'm really confused.

StarHalo said:

The lumen rating is the total amount of light coming out of the emitter, it's not the amount of light being placed on a specific area; since that light can be distributed any way, specifically a floody or thrower light, one light may put more lumens into the spill, another light may have a large hotspot, etc. You are emitting a total of 2700 lumens, just not in one confined area.

Also, you perceive differences in light levels by large leaps in percentages; you don't notice a difference at all until at least a roughly 10% change. Your combined light output is only about 40% over the Jetbeam's output, which you would perceive as modestly brighter at best.

Click to expand...

MDJAK said:

Did you mean to type 100 percent instead of 10? If not I'm really confused.

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No, a 10% disparity is what you need to see any difference at all - if I had a 2000 lumen and 2100 lumen light side by side, they would look exactly the same by the eye, even if you stared at them for several minutes, tried different comparison methods, etc. Yet if I compared 1 and 2 lumen lights, the 2 lumen model would look notably brighter.

That's the catch with high-output lights, it takes exponentially more lumens to "dazzle" you each time.

Please define your "light"
Light flux or brightness of hotspot
For brightness of hotspot a.k.a. lux, NO
It still depends on how they are distributed

For light flux a.k.a. lumen
Take xm-l as example
@700ma,2.9V lumen flux = 100% Power=2.03W
@1550ma,3.1V lumen flux =200% Power=4.805W
Double in flux < Double in power
So the answer is no

The myth is BUSTED

AnAppleSnail said:

Play with candles. The Jetbeam is 2 candles, the TK35 is 1. Put a table against the wall, stand a book up sticking out from the wall. Light 2 candles on one side and one candle on the other. Both sides of the book look well-lit, but where the light of all 3 reaches it doesn't look very much brighter. Where all 3 shine, it is 3x brighter than where one shines, and 50% brighter than where only 2 candles shine - you have 3 candles instead of 2. A good rule of thumb is that it is pretty hard to notice a 40% increase in light concentration.

Light concentration measures how much light there is per area. 3 candles is 3 times as many lumens as one. 'Lux' is lumens per square meter, or light concentration. The candle experiment compares 1x to 2x to 3x lux, and shows that even tripling light output isn't that dramatic.


The way the human eye works, you perceive light 'logarithmically.' That means that it takes a pretty big step up in light to look noticeably brighter. That is what you are noticing.

I mentioned 'light concentration,' lux, above. Flashlight output patterns are sometimes made to produce concentrated light, or a high lux value. This is great for seeing distant things, but not helpful for working up close. A bare lightbulb is all spread, and a focused searchlight will reach farther. Some people confuse higher lux with higher output.

Click to expand...

The game is different with LED, according to data sheet

jh333233 said:

For light flux a.k.a. lumen
Take xm-l as example
@700ma,2.9V lumen flux = 100% Power=2.03W
@1550ma,3.1V lumen flux =200% Power=4.805W
Double in flux < Double in power
So the answer is no

The myth is BUSTED

Click to expand...

What you're saying is that the XM-L is less efficient at 1550 mA than it is at 700 mA, which is not relevant to what the OP was really asking. Described in the terms that you're using, MDJAK's question was more like how much total luminous flux would two XM-Ls output if they were both running at 700 mA (100% for reference), and the answer would be 200% (while using less power for this level of output than a single XM-L would).

Yes, thats why i asked about his definition about light and power
Light? could be either lux or lumen
Power, can only be watts, by physics