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  1. #1
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    Riding in the fog

    Was out last night for a 3hr loop in JMP-Redwood-Chabot. The fog was really thick in a lot of areas and despite knowing the trails like the back of my hand, it was challenging to see if I was carrying any speed. I had a single (Strykr Pro) beam on the helmet and was wishing I had put it on the bars to get it a little lower.

    But it got me to thinking, why not have self-contained unit mounted on my (rigid) fork as a "fog light?"

    What are the best tactics to see at night in the fog? Especially when going in and out of it.

  2. #2
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    A lot of bike riders think that av StVZO-light (lights that have a beam with cutoff such as car headlamps) works the best.
    The best StVZO-light that I know of is the 80 Lux Philips light

    Read the test here: Philips SafeRide LED Bike Light – 2012 Mtbr Lights Shootout | Mountain Bike Review

  3. #3
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    The problem with the current crop of LED lights is that nearly all manufacturers use cool white tints, typically 6000K or more. HID lights suffer this too, halogens much less so. That heavy glare is due to the light internally reflecting and scattering within the droplets so some of the light comes straight back at you. You have pretty much sussed the tactics - lower angled beam and switch the helmet light off. Learn to accept lower speeds in dense fog, just as you should when driving.

    Light mfrs big up raw output in the lumen marketing wars but the quality of light seems to have been lost in the carnage. Eventually some of them will ping this, but don't hold your breath. Long term, one option is to buy from one of the custom lights builders and specify lower colour temperature LED's. Personally I prefer a mix of tints, but many still like the clarity that higher temp lights give. Glare in fog is the price you pay.

  4. #4
    nocturnal oblivion
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    Yellow. The old halogen lights work much better in the fog than the new LED's, as AlisterG points out.
    Maybe try a tinted film from a hobby shop, you'll lose lumens but it should cut through the fog better.
    "...like sex with the trail." - Boe

  5. #5
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    Quote Originally Posted by AlisterG View Post
    The problem with the current crop of LED lights is that nearly all manufacturers use cool white tints, typically 6000K or more. HID lights suffer this too, halogens much less so. That heavy glare is due to the light internally reflecting and scattering within the droplets so some of the light comes straight back at you. You have pretty much sussed the tactics - lower angled beam and switch the helmet light off. Learn to accept lower speeds in dense fog, just as you should when driving.

    Light mfrs big up raw output in the lumen marketing wars but the quality of light seems to have been lost in the carnage. Eventually some of them will ping this, but don't hold your breath. Long term, one option is to buy from one of the custom lights builders and specify lower colour temperature LED's. Personally I prefer a mix of tints, but many still like the clarity that higher temp lights give. Glare in fog is the price you pay.
    I initially believed that yellow lights were better in the fog due to the scattering effect. However, apparently there is no scientific basis for this, since the water droplets are so much larger than the wavelength of the light, scattering is quite uniform at that particle size.

    Still, my eyes don't like blue(ish) light, so I'll stick with a warmer tint if possible.
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  6. #6
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    So maybe there's is a reason to resurrect my old dual beam niterider from the late 90's

    Just need to find a new battery that isn't as much as a new light system...

  7. #7
    nocturnal oblivion
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    Quote Originally Posted by plantdude View Post
    So maybe there's is a reason to resurrect my old dual beam niterider from the late 90's

    Just need to find a new battery that isn't as much as a new light system...
    No joke, for foggy rides my old Light and Motion Halogen makes a world of difference.
    Maybe try a hobby store and find the colored films for model airplanes, they might have scraps.
    I use the red tape for vehicle taillight repair over my MS as a taillight. They probably have that in yellow as well but I think it's pretty dark. Just be careful about overheating if you try it, the MS w/ the red tape doesn't cause any problem though.
    "...like sex with the trail." - Boe

  8. #8
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    You're right, its not scattering (Rayleigh or Mie) but geometrical optics, due to fog particle size being greater than light wavelength. A longstanding study into different coloured car foglights claimed that the variation of colour temperature of the light had no significant effect on light transmission, yet the perception of less glare in lower colour temps remains. It seems to be the human eye's ability to perceive, not the actual transmission/reflection that counts.

    Very dry, dusty conditions are even worse with cool coloured lights for me. I still prefer coolish (but not blue tint lights) in clear air for clarity, but not for hazard spotting, where a mix of colours seems to pick out obstacles better. Tree roots blend into the rest of the ground in cool colours but a mix gives me a better perception of colour to distinguish between different trail surfaces and obstacles. Light manufacturers, take note...

  9. #9
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    Thanks for the replies.

    What about the concept of mounting the light as low as possible, similar to a vehicle fog light? With the explosion of bright self-contained lights, it seems feasible to mount a light towards the bottom of a fork leg (or would the wheel/tire block too much of the light)? Of course the brightness adjustment would be out of reach, but would this position improve visibility? Hmmm...seems like there might be a niche for a simple dual beam fog light system for bikes?

  10. #10
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    Yes, mounting low on the fork will help, but casts longer shadows so that small obstacles appear larger than they really are. Also, it sometimes appears to me that fog is less thick very close to ground level, less than 500mm. Perhaps some boundary layer effect is occurring? The torch mounting brackets on DX/KD/Manafont et al could be bodged to fit round the larger fork leg diameter.

  11. #11
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    fog

    I like to keep my lights off during the fog

  12. #12
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    You need 1 torch or something on each leg or the wheel casts a nasty shadow, yes I've tried it.

    Try blanking off some of the lense aswell, stop as much light as possible going up into the fog.

    The issue is though, even with small dips in the trail you get huge shadows depending on how low you go which can be quite scarey

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