Hi.  I'm in the throws of fitting front fog lights to my Mk2 Pre-FL, and I've been wondering about either All Weather or Selective Yellow (french-style) bulbs.  I'm fitting the lights because the last few days have been really foggy, and I've been caught out a couple of times in situations where I just cannot see the edges of the road.

 

I was wondering if anyone has tried selective yellow or all-weather bulbs in their fog lights, and if they have been any better than normal bulbs for visibility?  ABD sell selective yellow bulbs, and Halfords still stock their own brand and Bosch all-weather bulbs.

 

As a side note, I have Philips +150% bulbs in my headlamps, would I be able to see better in dense fog with normal output bulbs?  Once the fog lights are fitted, I know I will be able to run with just fogs to help this situation (when the weather makes it appropriate of course, not just when I'm wearing my baseball cap backwards).

"Yellow light is better in fog" is an urban myth.

 

High output headlights will be better in daylight fog but not in night-time.

I found this interesting:

http://www.danielsternlighting.com/tech/lights/light_color/light_color.html

 

I also have a pair of 'sports' yellowish-tinted sunglasses that I bought many years ago, and I find I can see better through daylight fog (and very heavy rain / motorway spray) if I wear them.

Daniel addresses how to get to Selective Yellow, and how to filter white generally, but doesn't really touch on the human factors beyond a few comments about blue light. The company I work for has a specialist Human Factors department, and they say that any benefit from SY fog lights over white ones using the same bulbs is down to the reduction in actual lumens output rather than the removal of the (small proportion based on Daniel's own figures) of blue/violet.

You do find a lot of rally cars using yellow lights when in snowy conditions due to how it reflects off the snow. 

I think the myth appears because when you hit your main beam in fog you cant see anything as it reflects off the fog, this is mainly due to the lights being designed to scatter higher up where as fog lights are designed to be low so they go under the fog

@ryan-re

It's not that the bulbs illuminate under the fog, that's all the way to ground level.

It's the difference in viewing angle.

Rather than looking along the main/dipped beams and seeing all the reflected light you are actually viewing the fog lamp beams from a more offset viewpoint and looking down on the illuminated fog with less reflected light.

@ryan-re

It's not that the bulbs illuminate under the fog, that's all the way to ground level.

It's the difference in viewing angle.

Rather than looking along the main/dipped beams and seeing all the reflected light you are actually viewing the fog lamp beams from a more offset viewpoint and looking down on the illuminated fog with less reflected light.

Half-right. That is correct as far as it goes, but wouldn't make much difference (any at all on Octy 1 and 1990s Audi A4 with fog lights in the headlamps) if the fog light beam wasn't much flatter topped than the headlight.

 but wouldn't make much difference (any at all on Octy 1 and 1990s Audi A4 with fog lights in the headlamps) if the fog light beam wasn't much flatter topped than the headlight.

 

Spot on with the description regarding the fog light within the headlight - I have these on my Merc Vito sport van and found out whilst travelling back from Glasgow usual run every week (fog one week @ Beatock & falling snow the next week @ Top of Shap), turned my headlights off to reduce the glare, fog lights on - just the same as having headlights on. What a waste of time - lighting to high up, needs to be lower down, closer to the ground the better.

 

Paul

Spot on with the description regarding the fog light within the headlight - I have these on my Merc Vito sport van and found out whilst travelling back from Glasgow usual run every week (fog one week @ Beatock & falling snow the next week @ Top of Shap), turned my headlights off to reduce the glare, fog lights on - just the same as having headlights on. What a waste of time - lighting to high up, needs to be lower down, closer to the ground the better.

 

Paul

They are way better than headlights (OK, I do have Nightbreaker+ bulbs in mine) on the Octy 1.

Fair enough.  So, next question - this suggests that I would be OK to use high-output +150% lamps in my fog lights, or should I stick with standard output?  In my last car, I had nightbreakers everywhere, including the low-mounted fog lights, but I didn't encounter fog quite as bad as I faced the other night.

Fair enough.  So, next question - this suggests that I would be OK to use high-output +150% lamps in my fog lights, or should I stick with standard output?  In my last car, I had nightbreakers everywhere, including the low-mounted fog lights, but I didn't encounter fog quite as bad as I faced the other night.

Sorry, my last was unclear. I have Nightbreaker+ in my headlights, and normal "white" H3s in my fogs. I don't see any point in fitting high output bulbs in fogs because they're about reducing dazzle off airborne water droplets and snow, not about range.