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Thread: Too Bright

  1. #76
    Senior Member alan s's Avatar
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    Quote Originally Posted by cyccommute View Post
    I've ridden in the DC area. There are alternatives. Even in the gridless east there are alternatives that parallel busy roads. Even the busy roads are still rideable to an experience cyclist.
    You're right. They're called trails around here: Mount Vernon Trail, Custis Trail, Capital Crescent Trail, Four Mile Run Trail, etc. All are used heavily by bikes, runners and walkers day and night. The alternatives are not nearly as safe, but you already knew that, having ridden in the DC area.

  2. #77
    Mad bike riding scientist cyccommute's Avatar
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    Quote Originally Posted by alan s View Post
    You're right. They're called trails around here: Mount Vernon Trail, Custis Trail, Capital Crescent Trail, Four Mile Run Trail, etc. All are used heavily by bikes, runners and walkers day and night. The alternatives are not nearly as safe, but you already knew that, having ridden in the DC area.
    If you are worried about how your lights affect other trail users as Darth Lefty stated in post 9, there are always nonbike path alternatives for night time use. I don't blind bike path users at night while running 3 very bright lights by not riding bike paths at night. I avoid using bike paths at night because 1) I don't want to be that jerk cyclists and 2) most paths around me aren't open after sunset.

    The paths are patrolled and nothing slows down your commute like being stopped and explaining to the police why you are on a closed path. Checking your ID, checking you background and writing a summons can take an hour or more. I'd rather get home.
    Stuart Black
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  3. #78
    Mad bike riding scientist cyccommute's Avatar
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    Quote Originally Posted by acidfast7 View Post
    but good luck getting people to understand that lumens don't matter, lux matters and where the lux is located should be regulated just like it is with an auto headlight
    I'm pretty sure you have me on ignore but here goes anyway: I've tried to explain this to you several times. Lux is a valid measurement but so is lumen output. Lux is not valid if you don't have a distance measurement. My 650 lumen lights have a lux measurement of 1.3 million. What does that tell you about the light coverage. It also has a lux measurement of 29 lux. Which measurement do you want to use? For bonus points, how far way from the source is each measurement?

    Just giving a lux number for a light tells you nothing about the light without the distance to the target. To put it in chemical terms, I have a reaction with compound A and compound B going to compound C. If compound A has a concentration of 4 moles per liter and compound B has a concentration of 2 moles per liter while compound C has a concentration of 6 moles per liter, how long has the reaction been going on and what was the starting concentration of A and B? You can't tell me because you don't have enough information. If I told you a rate constant, you could figure out the problem but without it you can't.

    Same holds for a lux measurement. Without knowledge of the distance to the target, the measurement is meaningless. If I have the lumens, I can calculate a lux at any point from the source to infinity. I can't determine if the light is bright or not based on just the lux measurement. A 29 lux light could be a 1 lumen light measured millimeters from the source or a million lumen light measured 10 km from the source. I can't tell and neither can you.
    Stuart Black
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  4. #79
    Bicycle Repair Man !!! Sixty Fiver's Avatar
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    My wife runs this on her commuter, at 40 lux it is the equivalent of a 3 watt LED and runs off a generator hub.

    The output is more than adequate to see and be seen, the daytime lights are excellent, and it has a high beam cutoff and standlight... the matching rear also has a standlight and voltage sensor that brightens the rear light at stops like a car or motorcycle.

    European lights now come in versions that have twice the output and one thing that sets them apart is their high quality lenses and high beam cutoff that keeps you from blinding other road users.

    I would like to take all these tactical flashlights and shove them where the sun doesn't shine and North American Cyclists shoulds be pushing for better regulations on bicycle headlights as it might get us a little more credibility and respect.

  5. #80
    What, me worry? Telly's Avatar
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    I'll second Sixty Fiver... have been running the following on my tourer with 60 lux and daytime running lights and am very satisfied with the spread of the beam and it's intensity. Whenever I use my tourer in the city with this light, I have people telling me that I've left my front lights on (the four bottom leds + 20% of the main led), which means that I can and am seen.



    I had to change my rear dyno light because of a capacitor fail, and opted NOT to get the brake-light function since I believe would confuse the already dazed and confused drivers where I commute. I ended up getting the following which cost next to nothing (around $18) and has a very bright light, seen for 320 degrees. It of course has a 4 minute stand-light function, but unfortunately no off switch, which I believe is needed when you reach your destination and don't want the rear light on when you've walked away from the bike.


  6. #81
    Bicycle Repair Man !!! Sixty Fiver's Avatar
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    Telly, I plan on getting a Cyo for my Moulton which rolls out a little faster than my wife's commuter... it is another great light.

  7. #82
    What, me worry? Telly's Avatar
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    Quote Originally Posted by Sixty Fiver View Post
    Telly, I plan on getting a Cyo for my Moulton which rolls out a little faster than my wife's commuter... it is another great light.
    Absolutely worth it's weight in gold, and I would suggest getting the T and not the RT, since the T is 60 lux verses 50 (rt), and throws the light a bit farther away. Just note that the T leaves a 2-3 foot "gap" from the unit to where the light touches the pavement, but this sounds worse than it is.

  8. #83
    http://www.538.nl acidfast7's Avatar
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    Quote Originally Posted by cyccommute View Post
    I'm pretty sure you have me on ignore but here goes anyway: I've tried to explain this to you several times. Lux is a valid measurement but so is lumen output. Lux is not valid if you don't have a distance measurement. My 650 lumen lights have a lux measurement of 1.3 million. What does that tell you about the light coverage. It also has a lux measurement of 29 lux. Which measurement do you want to use? For bonus points, how far way from the source is each measurement?

    Just giving a lux number for a light tells you nothing about the light without the distance to the target. To put it in chemical terms, I have a reaction with compound A and compound B going to compound C. If compound A has a concentration of 4 moles per liter and compound B has a concentration of 2 moles per liter while compound C has a concentration of 6 moles per liter, how long has the reaction been going on and what was the starting concentration of A and B? You can't tell me because you don't have enough information. If I told you a rate constant, you could figure out the problem but without it you can't.

    Same holds for a lux measurement. Without knowledge of the distance to the target, the measurement is meaningless. If I have the lumens, I can calculate a lux at any point from the source to infinity. I can't determine if the light is bright or not based on just the lux measurement. A 29 lux light could be a 1 lumen light measured millimeters from the source or a million lumen light measured 10 km from the source. I can't tell and neither can you.
    I know the difference between Lux and Lumens. Most reputable light makers list Lux over the areas and distances described in the German regulations, which state that certain areas at certain degrees and distances from the headlamp mounted at the particular height and angle relative to the ground.

    Therefore, I know that the light company has done the necessary measurements so that I know it works in a particular manner, hence I know that it's over a threshold performance.

    As far as lumens goes, it's just a crapshot measurement that doesn't state when the light actually goes. In addition, it's grossly exaggerated by most makers, because the US doesn't have a mandatory testing service that must be undertaken before a light enters the market. So, when I see lumens, I know that 99% of the time there's no quality minimum that has been surpassed.

    Yes, you're blocked as I find your comments distracting and really you want I'm totally bored.
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  9. #84
    Mad bike riding scientist cyccommute's Avatar
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    Quote Originally Posted by acidfast7 View Post
    I know the difference between Lux and Lumens. Most reputable light makers list Lux over the areas and distances described in the German regulations, which state that certain areas at certain degrees and distances from the headlamp mounted at the particular height and angle relative to the ground.

    Therefore, I know that the light company has done the necessary measurements so that I know it works in a particular manner, hence I know that it's over a threshold performance.

    As far as lumens goes, it's just a crapshot measurement that doesn't state when the light actually goes. In addition, it's grossly exaggerated by most makers, because the US doesn't have a mandatory testing service that must be undertaken before a light enters the market. So, when I see lumens, I know that 99% of the time there's no quality minimum that has been surpassed.
    I have seen few distance measurements with lux data. Sixty Fiver and Telly both list lux measurements without any reference to a distance measurement. Sixty Fiver even has a screen shot from a manufacturer that includes a lux measurement without a distance measurement. Perhaps there are standards out there that the manufacturers use but I haven't seen any reference to those standards. That makes the measurement as meaningless as most lumen claims.

    Quote Originally Posted by acidfast7 View Post
    ... really you want I'm totally bored.
    Huh?
    Stuart Black
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  10. #85
    aka Tom Reingold noglider's Avatar
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    cyccommute, some of us are happy with our lights, even though they are different from yours. It might pay for you to acknowledge that and also the fact that our reasons are not due to our ignorance or stupidity.
    You don't read my signature anyway, do you?

    Tom Reingold, noglider@pobox.com
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  11. #86
    Mad bike riding scientist cyccommute's Avatar
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    Quote Originally Posted by noglider View Post
    cyccommute, some of us are happy with our lights, even though they are different from yours. It might pay for you to acknowledge that and also the fact that our reasons are not due to our ignorance or stupidity.
    Your comment is completely uncalled for. Where in this thread have I said anything that could even be remotely construed as saying that people are ignorant or stupid? For that matter where have I said that people have to have lights that are just like mine? I never say that someone has to have lights like what I use. I may argue that some lights and lighting systems are inferior in other threads but I have never said that you have to use lights like mine.
    Stuart Black
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  12. #87
    aka Tom Reingold noglider's Avatar
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    Sorry. I must have misunderstood you. When some of us say why we like our lights, you point out a problem you have with them. I took that to mean that you feel we're overlooking something important.
    You don't read my signature anyway, do you?

    Tom Reingold, noglider@pobox.com
    Residences: West Village, New York City and High Falls, NY
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  13. #88
    Senior Member alan s's Avatar
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    Quote Originally Posted by noglider View Post
    Sorry. I must have misunderstood you. When some of us say why we like our lights, you point out a problem you have with them. I took that to mean that you feel we're overlooking something important.
    Your lights are brighter than you are?

  14. #89
    aka Tom Reingold noglider's Avatar
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    Quote Originally Posted by alan s View Post
    Your lights are brighter than you are?
    Perhaps! But for sure, cyccommute's lights must be brighter than I am!
    You don't read my signature anyway, do you?

    Tom Reingold, noglider@pobox.com
    Residences: West Village, New York City and High Falls, NY
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    OK calm down.
    Lux or lumens... the real problem is these metrics do not tell you how it will work for you under your riding conditions.

    Lumens usually means the total luminous flux emitted (in all directions), and Lux is lumens per sq meter (so where do you position that square meter).
    And light falls off with distance. What is not quantified is the shape of the emitted beam.

    If you want to ride at say 20 mph in total darkness, you need a very bright light to see both what's coming up and the obstacles.
    But a person on the trail/road coming toward you will be blinded by that much light.

    We need lights with more abrupt cutoffs so you can see the trail surface without blinding oncoming people.
    A helmet mounted light can be good because you can steer it away from oncomers.
    And, I use my helmet visor to block the bright lights coming toward me.
    I've been commuting 20 years, and the lights are MUCH brighter than they used to be.

    If you are in bright city lights in every direction, then you simply need very bright lights, or many lights, or luck to stay safe.

  16. #91
    http://www.538.nl acidfast7's Avatar
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    Quote Originally Posted by buzzbee View Post
    Lux is lumens per sq meter (so where do you position that square meter).
    And light falls off with distance. What is not quantified is the shape of the emitted beam.
    All of these, including the shape of the beam and intensities in different directions is quantified by German law

    http://swhs.home.xs4all.nl/fiets/tes.../index_en.html

    Some of it doesn't translate so well into English, but this guy gives it a shot and does complain that it's not precise enough.
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  17. #92
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    Quote Originally Posted by acidfast7 View Post
    All of these, including the shape of the beam and intensities in different directions is quantified by German law

    http://swhs.home.xs4all.nl/fiets/tes.../index_en.html

    Some of it doesn't translate so well into English, but this guy gives it a shot and does complain that it's not precise enough.
    I was on the train the other day and another guy had his bike with him. As he was taking it down from the head high peg that MAX trains have tor you to hang your bike from (by the front wheel) I noticed that his front brake couldn't possibly be working. I looked closer and sure enough. His front brake was trashed. He was riding around town on a bike with seriously degraded braking performance. No one is going to give a rats patootie unless he is creamed in an intersection that he couldn't stop for. If they even bother to find out what made an otherwise reasonable human being just ride out into rush hour traffic. Car lights in America and car and bike lights in Germany are regulated... I don't know about Europe but I can tell you that you can have the most scientifically calibrated low beam cut-off that automotive lighting science can devise but it all goes to hell if the mouthbreather driving the car, uses his high-beams in town at night. And many do. It makes little difference where the cut-off of the low beam is, if the mouthbreather driving the pick-up has lifted it so high that children and older adults riding with him need supplemental oxygen. Even low beams that high off the ground are going to blind oncoming traffic, and they do. So what does all that care and concern about beam width, cut-off, intensity, etc. mean in the real world of lax (non-existent) enforcement of roadgoing equipment?! I honestly don't think German style attention to bicycle lights will ever be a reality in the U.S. Not in yours and my lifetime.

    H

  18. #93
    http://www.538.nl acidfast7's Avatar
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    Quote Originally Posted by Leisesturm View Post
    I was on the train the other day and another guy had his bike with him. As he was taking it down from the head high peg that MAX trains have tor you to hang your bike from (by the front wheel) I noticed that his front brake couldn't possibly be working. I looked closer and sure enough. His front brake was trashed. He was riding around town on a bike with seriously degraded braking performance. No one is going to give a rats patootie unless he is creamed in an intersection that he couldn't stop for. If they even bother to find out what made an otherwise reasonable human being just ride out into rush hour traffic. Car lights in America and car and bike lights in Germany are regulated... I don't know about Europe but I can tell you that you can have the most scientifically calibrated low beam cut-off that automotive lighting science can devise but it all goes to hell if the mouthbreather driving the car, uses his high-beams in town at night. And many do. It makes little difference where the cut-off of the low beam is, if the mouthbreather driving the pick-up has lifted it so high that children and older adults riding with him need supplemental oxygen. Even low beams that high off the ground are going to blind oncoming traffic, and they do. So what does all that care and concern about beam width, cut-off, intensity, etc. mean in the real world of lax (non-existent) enforcement of roadgoing equipment?! I honestly don't think German style attention to bicycle lights will ever be a reality in the U.S. Not in yours and my lifetime.

    H
    This is a strange diatribe that pertains little to the discussion at hand.
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    I detect some connection to the discussion.
    Germany has regulations and specs on bike lighting, including specs on cutoff.
    The vendors can meet these specs and therefore sell to the market.
    But, it all breaks down if the user aims it incorrectly or ignores others.
    If the person does not care about others, there is probably little to be done, other than giving them some feedback.

    Another point is that if there were lights available that were both bright, and had a good cutoff, some of us would buy them and aim them correctly.
    I made my own collumator from a plastic lid, to help reduce light intensity where it's not needed, but it's not ideal.

    For those riders with very bright lights coming towards me in pitch darkness, I have my visor, ....

  20. #95
    Mad bike riding scientist cyccommute's Avatar
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    Quote Originally Posted by buzzbee View Post
    Lux or lumens... the real problem is these metrics do not tell you how it will work for you under your riding conditions.
    But both, with the proper information, can give you an idea of how they will work for you.

    Quote Originally Posted by buzzbee View Post
    Lumens usually means the total luminous flux emitted (in all directions), and Lux is lumens per sq meter (so where do you position that square meter).
    And light falls off with distance. What is not quantified is the shape of the emitted beam.
    What you say is partly true. Lumens are for the luminous flux in all directions...if the light isn't constrained. For bicycle lights all of them have some kind of reflector to constrain the light to a certain path.

    Light doesn't just "fall off with distance". Light intensity decreases in proportion to the square of the distance. So if the light has an intensity at point A of 1, if you measure the light at point B which is 2 times the distance of point A, the light isn't half as bright but the intensity decreases by 4 times. That's the problem with stating that only the lux of a light should be used for comparison. If you don't know how far away from the source the measurement is made, you can't really determine how much area is being illuminated. With lumens, you can calculate a lux...which is a useful measurement...at any distance. That will tell you a lot about how bright the beam will be. Without the distance measurement, you can't back calculate the lux for varying distances.

    On any beam, you can assume that the beam shape is going to be roughly round. Even with cutoffs, the beam will eventually assume a round shape since it is going to be spreading out in a cone from the source. It may take a little while to assume a conical shape but it will get there.

    Quote Originally Posted by buzzbee View Post
    If you want to ride at say 20 mph in total darkness, you need a very bright light to see both what's coming up and the obstacles.
    But a person on the trail/road coming toward you will be blinded by that much light.
    Hence my point about not riding on bike paths at night. If you are really concerned about "blinding" a fellow path user, don't do it. Even then "blinding", i.e. the complete loss of visual acuity, is too strong a word. You might cause someone looking at your lights discomfort but they aren't going to lose their eyesight completely.


    Quote Originally Posted by buzzbee View Post
    We need lights with more abrupt cutoffs so you can see the trail surface without blinding oncoming people.
    A helmet mounted light can be good because you can steer it away from oncomers.
    And, I use my helmet visor to block the bright lights coming toward me.
    I've been commuting 20 years, and the lights are MUCH brighter than they used to be.
    I disagree. Go stand a few dozen feet from in front of a car with an abrupt cutoff. The light is coming at you in a cone. You get a lot of upward spillage as an observer and the light will appear conical. If you are lower than the light source, the intensity of the light will increase. The world isn't flat and there are plenty of times when you might find yourself above an observer. A helmet light...something that I use...is even worse because the source is almost always higher than someone coming at you.

    As for light brightness, I have to disagree here too. LED lights are currently about where high end halogens were around 2000. You can force about 700 lumens from an MR11 halogen by overvolting it. LED emitters are currently putting out about that amount of light. If you go to an MR16 halogen, you can overvolt it and get out 1500 lumens from a single source. You can gang up several LEDs and get that kind of output but the throw of a single source 1500 lumen lamp is much, much further than that LED. Back when I used halogens, I could throw a coherent beam across Crown Hill Park lake and illuminate the trees on the other side of the lake. That's a distance of almost 0.5 miles. Haven't been able to do that with any LED I've used so far.

    Quote Originally Posted by buzzbee View Post
    If you are in bright city lights in every direction, then you simply need very bright lights, or many lights, or luck to stay safe.
    Just to show that I'm not always disagreeable, I wholeheartedly agree with you here.
    Stuart Black
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    I guess I should be happy that someone agrees with at least one thing I say....

    I agree with you that lux and lumens are good to know and compare.
    And agree that the distance from the source is required to give any meaning to the claimed light intensity.
    Of course, there is marketing... we do not always get that info. Others may disagree.

    I recall that the inverse square law applies to a point source of radiation.
    I'm pretty sure light falls off less rapidly when well focussed... (extreme case of shining a laser spot on the moon)...
    Any light source, at a sufficient distance, does behave as a point source (divergent beam)
    Others may disagree.

    Overall bike light brightness: I was refering to, then and now, the brightness with "off the shelf" bike lights.
    I think they are (on average) brighter now, due to LEDs and batteries. Others may disagree.

    It's probably true that a bike light cutoff would work best if all roads and trails were flat,
    so at 50 feet, the light intensity created in the first 2 ft above the ground was bright, and much less bright above 2 ft.
    Since the world is not flat, having a bike light cutoff is sometimes no help at all. Others may disagree.

    I like the idea of having a cutoff, I'm not saying to make them mandatory, just a choice.
    Others may disagree.

  22. #97
    aka Tom Reingold noglider's Avatar
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    cyccommute, I agree that lux ratings don't mean anything without specifying distance. I'm going to bet that bike light makers are assuming some sort of standard distance such as ten meters, which means that the ratings might very well have meaning.
    You don't read my signature anyway, do you?

    Tom Reingold, noglider@pobox.com
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  23. #98
    rugged individualist wphamilton's Avatar
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    Lest anyone believe that there is nothing here but arguments from irreconcilable opinions, I eagerly await a 1200 Lumen Cree XML T6 bike headlight (Amazon) to replace my Ultrafire, although the flashlight is performing acceptably. It was on someone's recommendation on one of these threads, I think cyccomute.

    I kind of believe the claimed 1200 lumens even, or close to at least, and even though it's vague for describing how well a light will illuminate the area of most interest, I'm pretty confident that illumination volumes are similar enough between headlights that a higher number (if it is realistic) will be relatively brighter in practice. So I am optimistic and all is not as dark as it may seem here.

  24. #99
    Mad bike riding scientist cyccommute's Avatar
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    Quote Originally Posted by buzzbee View Post
    I recall that the inverse square law applies to a point source of radiation.
    I'm pretty sure light falls off less rapidly when well focussed... (extreme case of shining a laser spot on the moon)...
    Any light source, at a sufficient distance, does behave as a point source (divergent beam)
    The inverse square law applies to all kinds of phenomena. Light happens to be one of them. The light propagates in a spherical wave front which increases in area as you move away from the source. The size of the wave front is related to the size of the aperture of the beam. A laser stays well focused because the radius of the aperture is very small so that the wave front stays small for a longer distance.

    Quote Originally Posted by buzzbee View Post
    Overall bike light brightness: I was refering to, then and now, the brightness with "off the shelf" bike lights.
    I think they are (on average) brighter now, due to LEDs and batteries.
    Niteriders of around a 2000 vintage...as "off the shelf" as you can get...were as bright or even brighter than the single emitter LEDs currently available. They were a MR-11 that was overvolted (about a 4.5 V lamp run at 6 V, if I recall correctly) so they pumped out more light then at nominal voltage. There were other 12 V systems available which put out 400 lumens at nominal voltage.

    Although no one used an MR16 in an off the shelf unit, there were plenty of home brew systems around that put out 800 lumens at 12V and a few tinkerers that made lights that put out the 1500 lumen lights. Halogens are power hogs, especially the MR11 but an overvolted MR16 has about the lumen per watt output as is currently available with LED. LED has the potential to go to a much higher lumen/watt output but they aren't there yet. I currently get about the same run time on the same amp-hour battery with LED as I did back in my days of halogen.

    Quote Originally Posted by noglider View Post
    cyccommute, I agree that lux ratings don't mean anything without specifying distance. I'm going to bet that bike light makers are assuming some sort of standard distance such as ten meters, which means that the ratings might very well have meaning.
    I agree that the distance is probably 10 meters but that's only speculation without further information. To state that the lux is the measure of light to use without knowing what the distance to the target is and further state that lumens is meaningless is a fundamental misunderstanding of the issue at hand. Yes, lumens are often inflated. But we know that and, from measurements that other people have performed as well as the specifications of the emitter, we can short through the chaff and get to the wheat.

    Lux is a measurement that could, potentially, be even more inflated than lumen measurement. As I showed above, I have a million lux light if I measure in the right place. Because the lux measurement is so distance dependent, even a little variation in the distance can throw the measurement off. For example, Telly says he has a 60 lux light. Assuming 10 m distance, that means that the light is pumping out 1300 lumens. I find that value a bit hard to believe. If the lux measurement is made at 5m, the lumen output of his light is 330 lumens...a value that is more believable.

    I went over to Peter White and looked at some of the Lumotec lights. He has a chart on the Luxos lamps. The claimed lux is 70 or 90, depending on model. At 10m, that's a lumen output for a dynamo lamp of 1500 lumens and 1971 lumens, respectively. I kind of doubt that you can get that kind of output from a dynamo. At 5m, the lamps have a lumen output of 380 lumens and 500 lumens, respectively. Both of those lumen values are more in the range of what I've seen for dynamo outputs.

    This just goes to show that assumptions can be tricky. They are often wrong.
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  25. #100
    Mmm hm! agent pombero's Avatar
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    I have 2540 lumens between my Niterider Pro 1800 and Cygolite Turbo 740. The NR is mounted on my helmet on flash mode, the power is amazing...it has the capability of freezing cars in time and space if I want to.

    That said, i am looking for a brighter 3000+ light in flash for the helmet, so that the Niterider can join the Cygolite on the handlebars to luminate the runway for me.

    Does the lupine betty have flash mode?

    Quote Originally Posted by thenomad View Post
    Whiny drivers complain when flashing lights disrupt their texting while driving. I say, that's the point.
    haha, I have thought the same thing! The brighter the better I say.


    Quote Originally Posted by ben4345 View Post
    When I say someone has their 600 + lumens light pointed right at my face on-coming traffic. It isn't nice at all.
    haha, 600 lums hurts your eyes? Playing in traffic is for the big boys and girls, where there are real dangers, with real lights coming from every direction. It looks like you can't handle it, ben.

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