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Post by hikerjer on Jan 30, 2020 19:14:55 GMT -8
OK, I basically know what a lumen is as measure of light. However, I just don't know how to judge how much light a specific set of lumens produce. Do I need 30 lumen, for a headlight or 100 for a bike headlight or what. I guess, What I'm asking is how do I determine how much relative light lumens actually produce?
Can anyone shed some light on this (sorry)?.
Thanks.
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texasbb
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Post by texasbb on Jan 30, 2020 20:02:12 GMT -8
Lumens is a measure of the total luminous flux (roughly, the amount of visible light coming out of a light source). How bright that is depends on the area of the surface over which it is spread. That brightness (illuminance) is measured in lux (1 lux = 1 lumen per square meter). So, the lumens you need depends on how wide-angle or focused the light beam, how far out you need to see, etc. And, it depends on your eyes and how well you see in the dark. In other words, I have no idea how many lumens you need.
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Post by johntpenca on Jan 30, 2020 20:07:02 GMT -8
noun The definition of a lumen is the measure of brightness from a light source. An example of a lumen is the 13 lumens of a candle and the 1,200 lumens of a 100 watt light bulb. Does that help? The ideal brightness for a bike light is between 300 to 600 lumens (google search). You are old, so I'd go for the 600.  Less for hiking. I'd think you would want separate lights for biking and hiking. Or combine a handlebar mounted light with a headlamp for night biking. Seems like you are over thinking it. |
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Post by hikerjer on Jan 30, 2020 20:43:26 GMT -8
The ideal brightness for a bike light is between 300 to 600 lumens (google search). You are old, so I'd go for the 600. Thanks, John, for that. It's the type of info I was looking for and I do appreciate you pointing out that I am old. Your powers of observtion are to be commended. Your time will come, grasshopper.  |
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franco
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Post by franco on Jan 31, 2020 0:55:34 GMT -8
This is a conversion table with something you might be more familiar with. Note that it is meant for people that understand aproximations (close enough is good enough...) and not at all for those that need exact and precise definitions.  |
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reuben
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Post by reuben on Jan 31, 2020 4:24:39 GMT -8
How bright that is depends on the area of the surface over which it is spread. This is crucial. Note that many headlights and even some bike lights have adjustable beams. So 100 lumens in a wide beam will cover a greater area but not as far, whereas the same 100 lumens in a narrower beam will illuminate farther at the expense of peripheral coverage. What you want will depend on the situation.
Flux is a key component, as mentioned above.
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ErnieW
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Post by ErnieW on Jan 31, 2020 5:10:59 GMT -8
One relationship to remember is that intensity is proportional to 1/distance squared. If you want to see twice far then you need 4 times the lumens.
So if your criteria is to see far ahead like cruising on a mountain bike then you need lots of lumens. If you need to just see where you are stepping hiking any lumens will probably do.
Besides the physics it also personal preference including how good your eyes are.
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Post by johntpenca on Jan 31, 2020 7:42:26 GMT -8
Thanks, John, for that. It's the type of info I was looking for and I do appreciate you pointing out that I am old. Your powers of observtion are to be commended. Your time will come, grasshopper. It's the pot calling the kettle black. We are the same age. |
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Post by hikerjer on Jan 31, 2020 9:08:36 GMT -8
It's the pot calling the kettle black. We are the same age. Close maybe, but I think I've got a few years on you. The proper respect and deference to your elders would be appropriate. :D |
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reuben
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Post by reuben on Jan 31, 2020 9:13:11 GMT -8
What do you want him to do, bring you your slippers? Without slobbering on them?
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Post by hikerjer on Jan 31, 2020 9:38:26 GMT -8
That would be nice- along with my glasses,and dentites.
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Post by georgeofthej on Jan 31, 2020 12:01:13 GMT -8
I've got a headlamp for backpacking with two brightness modes, plus a dimmer switch that can adjust the brightness in either mode. It's highly adjustable, but the dimmer is a little bit of a hassle to operate and I'd rather just have a button that cycles through 4 or 5 brightness modes.
Anyway, the brightest the thing goes is 60 lumens. I noticed that this is way brighter than I need for hiking on a good trail. But, the 60 lumens have come in handy when the trail becomes hard to discern and I need to look farther out. One example is that one time I was unsure where the trail went, I kicked the headlamp up to 60 lumens and saw a fallen tree with a segment sawed out the middle and knew that was the trail.
So for me 60 lumens is adequate for hiking. I've got no experience riding a bike at night, so I don't know how bright you'd go there.
BTW, I am also old.
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zeke
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Post by zeke on Jan 31, 2020 12:48:55 GMT -8
For a bike headlight, I'd look at burn time, also. Most I see are good for 60-90 minutes on high, which is about 600 - 1200 lumens depending on the model. If you never expect to be out in the dark for an hour, then any of them might work well, but a rechargeable one might be best in the long run.
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Post by hikingtiger on Feb 3, 2020 8:29:37 GMT -8
Especially through the capacitor...as you approach 88 mph. Or were you just looking for a good solder joint? Side note: there was a professor that filled in occasionally in my first semester of power systems that spoke with a serious lisp. Imagine the reaction the first time he was talking about transformers and mentioned "flux." |
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reuben
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Post by reuben on Feb 3, 2020 9:23:04 GMT -8
Especially through the capacitor...as you approach 88 mph. Or were you just looking for a good solder joint? As my calculus 3 professor used to say, "So you just create your favorite arbitrary 3 dimensional surface and calculate the flux through the surface." |
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