caught in thick fog......

So once a week i ride (bicycle) to work. its 25 miles one way, last week i got up early for the journey and looked out my window to see some truely awsomely thick fog ! for this i choose to mount up my olight m20 xp g2 - my most throwy light. it did 'ok' but really even with this i was really finding it hard to see anything. it only just cut through enough then when it got there the hot spot is tiny giving a very limited view.

it got me thinking what light should i have ? ( i had 25 miles to think about this ) compactish 18650. the best thing i can come up with is the armytek pred warm. is there anything else out there ? should i plump for a bigger reflector and xm l2 for a lot more light but matching throw ? - this would not be ideal due to the wind resistance but then i would only use it on these occasions not all year round.

thanks.

I recently got a Xeno F42 with XML2 neutral white which I quite like. It has pretty decent throw due to it's above average reflector size for its class with a decent size hotspot.
Worth a look and a bit cheaper than other offerings.
I actually use a custom triple in a small housing with external LiPo battery pack which is very compact overall but is more balanced flood/throw, the F42 while chunkier would out throw it pretty easily.

The brighter the light the more light that will be reflected back toward your eyes. You need something mounted down low so as less light is reflected directly to your eyes and lighting up just far enough for you to see clearly. As always slow down if your view is limited.

Norm

hey thanks for the move ! i really should look around the forums more oops .

i will look at the F42 thanks.

i didnt use my xm l lights because they would be floodier or have to greater spill ( think thats the bigger problem ) generally and white wash my view. mounting lower is interesting - i see what your saying there, i will have to play around with my mounts on the forks !

zs&tas said:

hey thanks for the move ! i really should look around the forums more oops .

i will look at the F42 thanks.

i didnt use my xm l lights because they would be floodier or have to greater spill ( think thats the bigger problem ) generally and white wash my view. mounting lower is interesting - i see what your saying there, i will have to play around with my mounts on the forks !

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Be very careful if you try to mount a light on your forks. Handlebar mounts will not be secure enough to prevent the risk of the mount rotating and suddenly the light gets caught in your spokes.....not a nice way to end a bike ride!!!

I would recommend a throwy warm or neutral light , but not too much output. I have had some success mounting lights under the handlebars, or to the side of the crossbar to get it as far off axis with my eyes as possible. Aim the light down so it is only lighting up the road no more than 5m away and go slowly.

Also make sure you have a very bright flashing rear light.

subwoofer said:

Be very careful if you try to mount a light on your forks. Handlebar mounts will not be secure enough to prevent the risk of the mount rotating and suddenly the light gets caught in your spokes.....not a nice way to end a bike ride!!!

I would recommend a throwy warm or neutral light , but not too much output. I have had some success mounting lights under the handlebars, or to the side of the crossbar to get it as far off axis with my eyes as possible. Aim the light down so it is only lighting up the road no more than 5m away and go slowly.

Also make sure you have a very bright flashing rear light.

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maybe something down under one of the barends would work and be safer. throwy and warm is why i thought the armytek predator r4 would be good. gd to here experiences !!

ugghhh... I hate fog!

The only thing worse than fog is riding at night in the rain, and that's mostly due to all of the light reflecting off of the road.

I haven't ridden in the fog at night though.... is that what we are discussing, or is this about riding in a heavy morning fog? My experiences have been with heavy morning fogs, and headlights weren't my main concern. My real concern was with the cars approching behind me at 60mph, and hoping that they saw me.

I use a bright steady taillight in conjunction with a Cateye LD1100 in flash mode. I've also used a white Lightman xenon strobe, which does a good job of throwing light in all directions. My assumption is that it may take a lot to penetrate the fog and let people know that I'm out there on the road.

Over the years, I've gotten more conservative about riding in low visibility conditions like this. My commute route is a narrow road with fairly fast traffic, and I'm not sure that they are really paying attention to the road. I'm inclined to just drive my car when the fog looks bad.

Steve K said:

ugghhh... I hate fog!

The only thing worse than fog is riding at night in the rain, and that's mostly due to all of the light reflecting off of the road.

I haven't ridden in the fog at night though.... is that what we are discussing, or is this about riding in a heavy morning fog? My experiences have been with heavy morning fogs, and headlights weren't my main concern. My real concern was with the cars approching behind me at 60mph, and hoping that they saw me.

I use a bright steady taillight in conjunction with a Cateye LD1100 in flash mode. I've also used a white Lightman xenon strobe, which does a good job of throwing light in all directions. My assumption is that it may take a lot to penetrate the fog and let people know that I'm out there on the road.

Over the years, I've gotten more conservative about riding in low visibility conditions like this. My commute route is a narrow road with fairly fast traffic, and I'm not sure that they are really paying attention to the road. I'm inclined to just drive my car when the fog looks bad.

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yep, i left mine at 5 am, dark here then. watch the sun get up ( lovely ) and its light when i get there at the mo. i do really want a rcr123 rear light, i think i will mod one to red then i will know it is always charged with my fronts.
thing is i left my house in the city in average fog, as i left the city thats when it got bad. hard to judge sometimes.

the xeno looks similar to my olight M22, with the wide spill i think i would just see white.....

Norm said:

The brighter the light the more light that will be reflected back toward your eyes. You need something mounted down low so as less light is reflected directly to your eyes and lighting up just far enough for you to see clearly. As always slow down if your view is limited.

Norm

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I like the mounting "down low" suggestion.

If I have read right: People used to think incans worked best in smoke or fog. Then, realized it wasn't the incan rather than some throw, combined with minimal output. The xr-c/xp-c fits this bill best? Is it not the highest throw per watt led? Sometimes, with too small hotspot for regular use-outside wall textural imperfection hunting. Also, most my (store purchased) xp-c's are probably 4000 kelvin.

degarb said:

The xr-c/xp-c fits this bill best?

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i dont know anything about these, i will look. if i take my m20 g2 thats 420 lumens - drops quick though over time, so if these can get anywhere near that it may be a good way to go.
thanks

zs&tas said:

i dont know anything about these, i will look. if i take my m20 g2 thats 420 lumens - drops quick though over time, so if these can get anywhere near that it may be a good way to go.
thanks

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You need a high lux with fewer lumens to punch through smoke and fog, per my understanding. A single xpc light can easily get 10,000 candela with a small reflector, for under $10 at Home Depot (flat output on 2 cell controlled Rayovac). Maybe three or 4, at that price. I have seen triple xp-c drop-ins, maybe lights.

For me, if it weren't for Lithium Colbolt 18650s, I might lean more to the xpc. The only 3 AAA light, I have ever used, worth using for even a half day with out hacksawing in a 3 AA pack, is xp-c based. That is how good the throw is.

degarb said:

I like the mounting "down low" suggestion.

If I have read right: People used to think incans worked best in smoke or fog. Then, realized it wasn't the incan rather than some throw, combined with minimal output. The xr-c/xp-c fits this bill best? Is it not the highest throw per watt led? Sometimes, with too small hotspot for regular use-outside wall textural imperfection hunting. Also, most my (store purchased) xp-c's are probably 4000 kelvin.

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I tested all these things years ago:

http://swhs.home.xs4all.nl/fiets/tests/verlichting/experimenten/index_en.html

Results: Warm white is best, neutral is almost the same as cool white, but the difference of cool/neutral with warm white is not great.

Throw is also not really an issue, in that you can't improve on it: what more throw a lamp normally has, does not translate into more throw in fog. You simply hit a certain limit and whatever power you throw at it, will not help to get more throw.

This was also shown by a Lupine Betty running at 10% vs. 100% power: Result: Almost no difference in what I could see, how far I could see. IIRC it was ca. 30m in that test for both 10% and 100% whereas I can see 75-80 m with it normally at full power.

Difference from eyes to lamp should be at least ca. 35cm, beyond that any 'wall of light' phenomenon drops of to almost nothing very quickly. So even a bar mounted lamp is fine. I noticed no wall of light using a Betty at full power on the bar...

Narrow or wide beam: As long as the lamp puts out a fair amount of light and as long as it's not like a laser : This is also not that important because all the light get scattered everywhere anyway.

Cutoff vs non-cutoff beams: Cutoff beams have no advantage here...

is there any published data on the effect of different light designs or configurations on visibility? i.e. what's the best strategy to not be run over? I've been working with my personal observations, which are simply that power is good, and a bright strobe can get people's attention.

Someday, I'd like to make a white or amber LED equivalent of the xenon strobe that I've been using, with better mounting options. I don't go out into heavy fog intentionally, but there are times/areas where the fog dramatically increases in density for no obvious reason.

swhs said:

I tested all these things years ago:

http://swhs.home.xs4all.nl/fiets/tests/verlichting/experimenten/index_en.html

Results: Warm white is best, neutral is almost the same as cool white, but the difference of cool/neutral with warm white is not great.

Throw is also not really an issue, in that you can't improve on it: what more throw a lamp normally has, does not translate into more throw in fog. You simply hit a certain limit and whatever power you throw at it, will not help to get more throw.

This was also shown by a Lupine Betty running at 10% vs. 100% power: Result: Almost no difference in what I could see, how far I could see. IIRC it was ca. 30m in that test for both 10% and 100% whereas I can see 75-80 m with it normally at full power.

Difference from eyes to lamp should be at least ca. 35cm, beyond that any 'wall of light' phenomenon drops of to almost nothing very quickly. So even a bar mounted lamp is fine. I noticed no wall of light using a Betty at full power on the bar...

Narrow or wide beam: As long as the lamp puts out a far amount of light and as long as it's not like a laser : This is also not that important because all the light get scattered everywhere anyway.

Cutoff vs non-cutoff beams: Cutoff beams have no advantage here...

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wow thank you for all that info swhs. very interesting stuff. i was surprised how little i could see with my M20, in the clear it fires a fair way. maybe i just did hit that barrier and nothing else would have helped. hmm.

steve K i see there are a lot of lazer rear red lights might be of interest ? ..

I wonder if fog and fire smoke act the same in how they scatter light. If so, maybe fog conditions could be reproduced by lighting a fire (putting it out with water), to test your light setup before taking it into the field.

degarb said:

I wonder if fog and fire smoke act the same in how they scatter light. If so, maybe fog conditions could be reproduced by lighting a fire (putting it out with water), to test your light setup before taking it into the field.

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i think this would be fun but i dont think it would be representative, Fog is basically water drops, clear and scattering light everywhere. the smoke is dust and is stopping light or absorbing light but not as much scatter im guessing.
i think higher power in smoke would help but not in fog.

zs&tas said:

i think this would be fun but i dont think it would be representative, Fog is basically water drops, clear and scattering light everywhere. the smoke is dust and is stopping light or absorbing light but not as much scatter im guessing.
i think higher power in smoke would help but not in fog.

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Smoke itself might not be good enough, depending on particle size, but you can simulate fog with smoke.

I have done but it was not on purpose

For example I had some toast burnt so bad that the whole lower floor of my house was full of smoke. The smoke itself after a while was no longer visible, and then a bit later I took a shower and instantly the whole bathroom was like fog (this is unlike normal water vapour under the same circumstances without smoke particles in the air).

Problem is for testing you need a big space, I mean to test for what distance you can see, you need a room of more than 30 metres long... But in principle, for any companies that would want to do fog testing it should be feasible: Create smoke, then inject water vapour into the air, vapour will condensate around the smog particles. Perhaps a very long hallway would be possible.


Throw: It was quite surprising that the difference between Betty at 10% and 100% was about nothing. The limit seems to be based on the fog, and not the amount of light you throw at it. Now suppose you increase the light from 1800 lumen of the Betty to 10 times that. What will happen? I think still throw will remain about the same because what happens is that the brightness of everything close to you gets increased a lot, so you get 'blinded' by the high intensity of the light close to you (this would perhaps be similar to what happens when you have a helmet mounted headlamp in the fog which can cause a 'wall of light' phenomen, it looks as if you then look through a very bright white fog. It is also similar to the effect of overexposure of the near-field that a lot of circular symmetric lamps have and which some asymmetric lamps have.

Here's my theory about fog...

• Fog is made up of water droplets, roughly spherical
• Tiny spherical beads are used for many retro-reflective materials (eg roadsigns)
• Therefore Fog reflects your own light back at you because it is also retro-reflective
• Smoke is not the same as fog, it is NOT retro-reflective, soot particles don't behave in the same way.
• Retro-reflective materials reflect light back directly towards the source of the light
• To stop being blinded by retro-reflective materials, move the light source laterally as far away from your eyes as possible.
• In fog lamp placement it is normal to move the light source to be as low as possible, but really that's the same idea as moving it laterally to be as far from your eyes as possible, you could move it up, down, left or right and get the same improvement.

One thing that I would like to suggest is to try putting a polarizing filter in front of the light source and rotating it to see if you can get in improvement. The water droplets are likely to be ovoid rather than exactly spherical due to the pull of gravity, and some of the light they reflect may therefore be polarised by that shape, and be prevented effectively by a polarizing filter.

I do remember when the old (very -- over a decade ??) ProPolymer Luxeon came out it was sold to firefighters for its penetrating beam. Because of the tight beam not as much light was reflected back in smoke.
It was, for its time, an amazing thrower. Still is actually.

All that to say....you may want to search around to see what firefighters use. But screenclene is right about fog being different than smoke.

Steve K said:

I've also used a white Lightman xenon strobe, which does a good job of throwing light in all directions.

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Xenon strobes illuminate the entire visual field, and have no beam that can be easily traced back to the source. They'll know you're there, but don't know exactly where. This is a recipe for hurting.

swhs said:

Cutoff vs non-cutoff beams: Cutoff beams have no advantage here...

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A beam with a good vertical cutoff is to your advantage. This is why low beams in a car are already better than high beams when in heavy fog.

The visual disturbances from either smoke or fog can be lessened by either using a selective yellow light, or wearing selective yellow goggles (it doesn't matter where the light filtration occurs, it's the light your eyes receive, not the interaction of whatever wavelengths of light there are with the fog).

A very bright, stead-burning red lamp might be best for the left-rear of the bicycle, like a rear fog lamp for a car.