Cyclists blinding drivers!

geordiefella

interesting thread

as much of my commute / training riding is on roads i chose the exposure strada and have a buton that dips and floods the beam as necessary. 480 nicely placed lumens. lasts about 6/8 hrs of mixed use before its less than half load and needs a charge of an evening.

the other nice thing is, unlike the ay ups, which a very nearly bought, it unclips really quickly for stowing in my bag once i've locked up at work.

daniel_b

geordiefella wrote:

the other nice thing is, unlike the ay ups, which a very nearly bought, it unclips really quickly for stowing in my bag once i've locked up at work.

Do you have an external battery on yours geordiefella?

In defence of the ayups, it probably takes me about 30 seconds to wrap the velcro strap around the stem, and put the light on the mount, and secure the rubber strap, and plug it in.

Cheers

Dan

geordiefella

No, the strada has an internal lithium. There is an external add on. I've got a single add on for rear exposure red eye.
The light dipping button swung it for me after seeing them for real at cycle show London last year.

hamboman

UndercoverElephant wrote:

Not sure about that, even the most basic car headlight kicks out about 1500 lumens, HID ones are over twice that. My torch is pretty bright, and it only manages 230. I do agree though that some people need to point them down a bit, but really, the brighter the better.

Bike lights can measure pretty highly in lumens, but only because the beam is very focused. Car lights produce a much greater total amount of light because they cover a wider angle while similtaneously focusing on specific points. Lumens are defined by the candela (luminous intensity) and the angle that intensity is focused into.

Bike lights: Small angle and moderate candela equals high luminous.
Car lights: Wide angle and very hight candela equals high luminous.

simple!

flynn160603

scottgeniusltd2005 wrote:

brighter is better. blind them they will slow down. if they slow down they don't hit you.

Sorry but your wrong.....a driver who is temporarily blinded by any kind of light could do all manner of things including loosing control of the car, imagine turning a corner and being blinded by a bike light while driving a car you could try and swerve to miss something and have an accident.

I use a bike light which is powerful enough so that I can see where i'm going along side a cheap cateye flashing front light so that people can see me, I really dont see the point of mega bright lights, I'm more concerned about people seeing me from behind to be honest,

If you think you have a really bright light show some consideration for other road/tow path users and dip the light to the ground a little

jedster

Yeah, I'm with flynn. On the road, I don't see that mega bright lights really help. A moderate power light with some low power flashers will get you seen without dazzling anyone. Offroad is different because you need a much more detailed view of the trail surface ahead.

Of course, if your high power light is well angled it is no problem to anyone - knock yourself out. But please make sure they are not pointing into people's eyes - that is obnoxious and counter-productive.

I also get annoyed by high power flashers. Low power is enough to get noticed. High power flashers play absolute hell with night vision - pupils seems to strobe just too late behind the flash to retain vision.

Oh, and comparing brightness with car lights can be misleading for the reasons noted above - they are generally well directed and the light is less focused. That said, some of the HiD lights in 4x4s are pretty obnoxious just because they are higher off the ground.

J



J

supersonic

hamboman wrote:

UndercoverElephant wrote:

Not sure about that, even the most basic car headlight kicks out about 1500 lumens, HID ones are over twice that. My torch is pretty bright, and it only manages 230. I do agree though that some people need to point them down a bit, but really, the brighter the better.

Bike lights can measure pretty highly in lumens, but only because the beam is very focused. Car lights produce a much greater total amount of light because they cover a wider angle while similtaneously focusing on specific points. Lumens are defined by the candela (luminous intensity) and the angle that intensity is focused into.

Bike lights: Small angle and moderate candela equals high luminous.
Car lights: Wide angle and very hight candela equals high luminous.

simple!

Lumens is total luminous flux emitted - changing beam spread and angle does not effect lumen output if the optics are the same efficiency.

bugsterboy

The Hundredth Idiot wrote:

I just won a pretty fancy Lupine Tesla 4 (see other threads) which puts out 700 lumens and am a little concerned about this. My only riding in the dark is on London roads and I wonder whether the benefit of having a really bright light is out-weighed by the anti-social effect.

Still, there are plenty of car drivers out there who drive around with badly adjusted headlights which are more blinding than my little, battery-powered thing could be.

I bought the same light last year and do sometimes worry about this.. I've not yet had any complaints though. As you may know the tesla has 4 settings, BRIGHT, mid, low and flashing. I'm sure the flash setting is set to the BRIGHT and theres no way of adjusting it. I just point mine a few feet infront of my wheel. Guess the only way to know for sure is to set up a test with a mate riding your bike, you in a car... But I'm not that organised lol...

hamboman

supersonic wrote:

hamboman wrote:

UndercoverElephant wrote:

Not sure about that, even the most basic car headlight kicks out about 1500 lumens, HID ones are over twice that. My torch is pretty bright, and it only manages 230. I do agree though that some people need to point them down a bit, but really, the brighter the better.

Bike lights can measure pretty highly in lumens, but only because the beam is very focused. Car lights produce a much greater total amount of light because they cover a wider angle while similtaneously focusing on specific points. Lumens are defined by the candela (luminous intensity) and the angle that intensity is focused into.

Bike lights: Small angle and moderate candela equals high luminous.
Car lights: Wide angle and very hight candela equals high luminous.

simple!

Lumens is total luminous flux emitted - changing beam spread and angle does not effect lumen output if the optics are the same efficiency.

Changing the spread does change the lumens, because it's a measure of rediant flux the human eye can see. Here is the formula: 1 lm = 1 cd·sr

So if you increase either the candela or the angle, lumens will be increased.

supersonic

1 lm = 1 cd·sr

Yes, but if you change the angle (sr) you naturally change the candela measurement as the flux is going over a wider or narrower angle.

Lumens is a measure of total luminous flux picked up by a sensor - this is unchanged if you alter the angle. Changing the angle changes the candela (and spot lux froma reflected surface), but not the lumens.

hamboman

no, you change the lumens

1lm = 1cd . sr

compare it to force = mass x acceleration
(bear with me!)

the force changes when either mass or acceleration changes.

likewise, with 1lm = 1cd . sr, the lumens MUST change when either cd or sr do. The formula says it must.

dilemna

The problem round here is getting cyclists to use any lights and cars to have more than one headlight illuminated :evil: .