Flashoholic223
Newly Enlightened
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- Mar 29, 2014
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feel free to add any helpful information!!:twothumbs
what is flux and do you want high flux in a light?
- Thread starter Flashoholic223
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dc38
Flashlight Enthusiast
Flux is quantifiable but not exactly qualifiable...it's usually measured in Electrical studies. The luminous "equivalent" would be lux, maybe?
bondr006
Flashlight Enthusiast
I'm sure the op means lux. And yes, the higher the lux....the farther the light throws its beam out.
StarHalo
Flashaholic
Luminous flux = lumens. Lumens is the gross [visible] output of the light, "how much light there is". A candle flame is 13 lumens, a car headlight is 500 lumens.
GordoJones88
Flashlight Enthusiast
SimulatedZero
Enlightened
Lol, alright. Flux can be defined as constant change or the rate at which something changes.So yes, you want lots of flux in a light.
As StarHalo already stated, luminous flux is measured in lumens. Most modern flashlights are going to advertise their highest lumen output some where on the package. Here's the thing with that, there's more to perceived brightness than lumens. Light output is also measured in candlepower. To keep things simple we are just going to stick with those two terms. Essentially, candlepower is a measurement of how much of the light has been focused down into a spot. How intense the light is. Lights with higher intensity will light up objects further away than less intense lights.
Here's the part where perception starts to kick in and everything becomes relative. More intense lights can appear to be as bright as less intense lights that have a higher lumen output. So a light with 200 lumens and 3300 candela, candlepower, would appear to be very similar to a light that is 400 lumens at 3100 candela. The main difference between the two is the light with the higher lumens per candela will light up a larger area at one time. In other words, it would be more like a flood light. Another difference is that the 200 lumen light could have a longer runtime at that setting because it draws less power to get there. This depends mainly on which LED the light is using. In example, the Fenix LD22 has ~215 lumens for around 2 hours and the Foursevens QP2A-X has ~400 lumens for about an hour. It's way more complicated than I just made it out to be due to the number of variables between the testing methods of both of those lights and the LED type. But, you can pretty much bet that higher output = less runtime as a general rule.
Now, you can use this to get an idea of the beam pattern of a light before you buy one. In example a Fenix TK41 is ~900 lumens and about 60,000 candela. You know that it's going to be a spot light with that much candlepower. A Fenix PD35 has ~960 lumens and about 10,000 candela. That light is going to be more of a flood light like your car's headlights. Lights everything up at once. So, a 150 lumen light focused to 6k or 7k candela can be more useful than a 500 lumen light focused to 3k candela. The 150 lumen light will run longer and still do very well for lighting things up. Example: Fenix E21 vs any small EDC light on direct drive with a Li-Ion battery.
Now, here's where it really gets sticky. 200 lumens does not appear to be twice as bright as 100 lumens. It takes 3 times the amount of light to appear twice as bright. Same thing with intensity. Have a 200 lumen light? A 400 lumen light with an equal percent increase in intensity will be a decent bump up. Nothing too exciting, but noticeable for sure. Could be the difference between "not quite enough" and "ah, there we go". Have a 200 lumen light with 3k cd (candela). Switch to 1000 lumens and 24k cd and your going to notice it a whole hell of a lot. Switch from that 200 lumen light to 900 lumens at 60k cd and your eyes are not going to like you.
Both intensity and over all brightness are major factors in perceived brightness. Each type of light, high intensity or low intensity, high output or low output, has their place. But, the biggest thing to remember is that it takes more and more light to keep appearing brighter. That's why mode spacing tends to be 5 - 35 - 100 - 350 - 900. That's what it takes for our eyes to keep seeing the difference.
Anyways, hope that helped
As StarHalo already stated, luminous flux is measured in lumens. Most modern flashlights are going to advertise their highest lumen output some where on the package. Here's the thing with that, there's more to perceived brightness than lumens. Light output is also measured in candlepower. To keep things simple we are just going to stick with those two terms. Essentially, candlepower is a measurement of how much of the light has been focused down into a spot. How intense the light is. Lights with higher intensity will light up objects further away than less intense lights.
Here's the part where perception starts to kick in and everything becomes relative. More intense lights can appear to be as bright as less intense lights that have a higher lumen output. So a light with 200 lumens and 3300 candela, candlepower, would appear to be very similar to a light that is 400 lumens at 3100 candela. The main difference between the two is the light with the higher lumens per candela will light up a larger area at one time. In other words, it would be more like a flood light. Another difference is that the 200 lumen light could have a longer runtime at that setting because it draws less power to get there. This depends mainly on which LED the light is using. In example, the Fenix LD22 has ~215 lumens for around 2 hours and the Foursevens QP2A-X has ~400 lumens for about an hour. It's way more complicated than I just made it out to be due to the number of variables between the testing methods of both of those lights and the LED type. But, you can pretty much bet that higher output = less runtime as a general rule.
Now, you can use this to get an idea of the beam pattern of a light before you buy one. In example a Fenix TK41 is ~900 lumens and about 60,000 candela. You know that it's going to be a spot light with that much candlepower. A Fenix PD35 has ~960 lumens and about 10,000 candela. That light is going to be more of a flood light like your car's headlights. Lights everything up at once. So, a 150 lumen light focused to 6k or 7k candela can be more useful than a 500 lumen light focused to 3k candela. The 150 lumen light will run longer and still do very well for lighting things up. Example: Fenix E21 vs any small EDC light on direct drive with a Li-Ion battery.
Now, here's where it really gets sticky. 200 lumens does not appear to be twice as bright as 100 lumens. It takes 3 times the amount of light to appear twice as bright. Same thing with intensity. Have a 200 lumen light? A 400 lumen light with an equal percent increase in intensity will be a decent bump up. Nothing too exciting, but noticeable for sure. Could be the difference between "not quite enough" and "ah, there we go". Have a 200 lumen light with 3k cd (candela). Switch to 1000 lumens and 24k cd and your going to notice it a whole hell of a lot. Switch from that 200 lumen light to 900 lumens at 60k cd and your eyes are not going to like you.
Both intensity and over all brightness are major factors in perceived brightness. Each type of light, high intensity or low intensity, high output or low output, has their place. But, the biggest thing to remember is that it takes more and more light to keep appearing brighter. That's why mode spacing tends to be 5 - 35 - 100 - 350 - 900. That's what it takes for our eyes to keep seeing the difference.
Anyways, hope that helped
lwknight
Enlightened
That is a very nice explanation to help put things in perspective for the pre-savvy readers.
I wish everybody was light savvy so at least we might get good flashlights at work but the tool room still issues 6 volt lanterns that might be 50 lumens and a tiny spot. My 3 AAA headlight out performs it at least 10X. As far as usefulness goes that is.
I wish everybody was light savvy so at least we might get good flashlights at work but the tool room still issues 6 volt lanterns that might be 50 lumens and a tiny spot. My 3 AAA headlight out performs it at least 10X. As far as usefulness goes that is.
