Red LEDs behind red lens?

Answer is "maybe". The lens is red because it filters out almost all other frequencies of light except red. Attenuation is minimum, but not zero. The other part of maybe is that it also depends upon the strength of the red leds themselves.

Easiest is try it and see.

Probably not, but not becuase of the lens but because LED "bulbs" just aren't bright enough. HAven't found one yet that works worth a crap, although I haven't tried any of the $40+ ones.

nate

IMO, they will not be seen from outside of a very narrow cone and won't be bright enough unless the tail light lenses are specifically made for leds.

No, it won't be, but it has nothing to do with the color. You _have_ to use a red LED if you have a red lens.... no other color will work.

But, you'll find the LED replacement bulbs in general have very poor dispersion and are harder to see than conventional incandescent bulbs. They're getting better all the time, but wait another few years before you go that route.

--scott

snipped-for-privacy@panix.com (Scott Dorsey) wrote in news:gnnid2$o3c$1 @panix2.panix.com:

Ain't that the truth.

Some time ago I was in heavy traffic behind this young kid in one of those Rice-a-roni Civics that sits a bouncy 1/16" off the pavement.

At first I thought I was not paying enough attention after having almost rear-ended him a couple of times, but then I realized the near-misses were due to his combination of Altezza-type aftermarket taillamps and LED brake lamp "bulbs". Those LEDs (eight per "bulb") were virtually invisible, and this in early-morning sunlight. Bet he thought he was super-kewl, though.

Maybe ten years...

I just did an experiment with a white LED flashlight,* and indeed, a red light emerges from a red taillight lens.

It's attenuated quite a bit. I've seen dimmer taillights in cars that perhaps had sorry electrical connections or a poor choice of bulbs, but still, it isn't nearly as bright as a properly selected and functioning incandescent taillight.

I guess the physics interpretation is that the LEDs might be more narrowband than incandescents but aren't lasers either; and the taillight lens is colored but isn't exactly a steep-sided, narrow notch filter.

--Joe

• Talk about the best thing you can do for safety for .99 at the discount tool bin near the cash register... they're small enough and cheap enough to have one or two in every car, and are quite bright.

I wasnt sure what he meant by that post either, but didnt challenge it. There should be some attenuation, since "white" light is composed of a distribution of wavelengths, essentially all of which but red would be filtered out.

Even 'pure' red light would suffer some attenuation, but not as much as white.