Coloured bulbs behind coloured lenses

[TheOtherLeft]

Is it OK to use coloured bulbs behind coloured lenses, eg brake or turn indicators?

I have a few dead bulbs in my brake lights (top mounted brake lights) and can buy T10 bulbs clear and coloured for the same price.

I've read that using coloured bulbs behind coloured lenses produces a "richer" colour but from my tangential experience I can't read red inked writing if using a red torch as the wavelengths cancel each other out. Does this make sense? Are these two phenomena the same?

Cheers.

 

[-Virgil-]

It'll drop your intensity, which you don't want to do. Use the correct bulbs for the application: colorless bulbs behind red or amber lenses, amber bulbs behind colorless lenses.

 

[Alaric Darconville]

Use the clear bulbs. If the color of the bulb differs slightly from the color of the lens, you'll lose more light than with a clear bulb in the first place (and still lose a little light anyway, since the tinting, even if perfectly matched, results in some light loss).

I can't read red inked writing if using a red torch as the wavelengths cancel each other out.

No, the white page reflects all the light (which is red), and the red ink reflects the light, so you're actually seeing the text (but you can't see the forest for the trees, in a manner of speaking). Nothing cancels anything out, it's just that your eyes are getting nothing but red light back from the entire scene, and so there's no contrast.

 

[Diesel_Bomber]

You'll definitely lose brightness, but it's not a total disaster to use a colored bulb behind a colored lens, depending on the color of the bulb and the color of the lens. Amber bulb behind red or amber lenses, fine. Red behind red, fine. Red behind amber will still look red. Blue or green behind amber or red lenses and you might as well not bother.

I've put an amber bulb behind a red lens, I honestly couldn't tell the difference between the side of the trailer with a clear bulb and the side with the amber bulb. My eyes and head are not calibrated light meters, I'm sure there was a difference, I just couldn't see it.

Before you lighting Nazi's pounce, the only options that dark and stormy night were 1.) Use the amber bulb, or 2.) Not have light on that side of the trailer. I chose the safer option.

 

[Hamilton Felix]

That's understandable. I've often carred a "natural amber" yellow bulb in my spares, figuring that if I had a broken lens, at least I wouldn't end up with a white light on the rear. And it would work fine on front marker lights.

 

[Alaric Darconville]

Before you lighting Nazi's pounce, the only options that dark and stormy night were 1.) Use the amber bulb, or 2.) Not have light on that side of the trailer. I chose the safer option.

For an emergency, sure-- use an NA or red bulb behind a red lens.

But when you're able to shop for bulbs and the selection is available (as in the OP's case) get clear bulbs for use behind colored lenses, and colored bulbs (where specified) behind clear lenses.

And buy spares.

 

[-Virgil-]

For an emergency, sure-- use an NA or red bulb behind a red lens.

...except you'd be very hard pressed to find a legitimate red bulb.

 

[Alaric Darconville]

B-b-b-b-ut I saw them at Wal-Mart!

Me, I'd never buy a red bulb for my own car, but if I'd burned a taillight out and dug around and that was the only available spare, it'd be SOMETHING to get me to the next gas station to get the right kind.

 

[Kuryakin]

But, why would you want to?

Is it OK to use coloured bulbs behind coloured lenses, eg brake or turn indicators?

I have a few dead bulbs in my brake lights (top mounted brake lights) and can buy T10 bulbs clear and coloured for the same price.

I've read that using coloured bulbs behind coloured lenses produces a "richer" colour but from my tangential experience I can't read red inked writing if using a red torch as the wavelengths cancel each other out. Does this make sense? Are these two phenomena the same?

Cheers.

 

[Hamilton Felix]

...except you'd be very hard pressed to find a legitimate red bulb.

Go to a big truck stop. You'll find red, blue, green, purple, just about any color you can name.

I can see a point to having a red bulb in the spares box, for the same reason I sometimes carry a natural amber bulb. You won't get the brightest light from that colored bulb, but you will be able to produce the legally required color if you happen to break a lens. That will get you home so you can fix it right.

 

[Alaric Darconville]

...except you'd be very hard pressed to find a legitimate red bulb.

Go to a big truck stop. You'll find red, blue, green, purple, just about any color you can name.

Key word being "legitimate". I searched store.candlepower.com and found only a few red bulbs, which appeared to be designed for specific purpose lights (one being a PAR36)-- if there were going to be a store carrying a legitimate red bulb, it'd be that one.

Also found were the 1156 & 1157. I'd guess that what they have is probably better than what you'll find at the Flying J.

Again, though, I probably would stick in a red bulb behind a broken taillight temporarily to get me home, rather than have no light at all (and to reduce white light being thrown into a driver's eyes behind me at night).

 

[-Virgil-]

Go to a big truck stop. You'll find red, blue, green, purple, just about any color you can name.

Ahem: legitimate. None of the ones you're talking about is legitimate. They don't put out the right color of red light, they don't put out the right amount of light, and their filament position can't even be commented on because the filaments aren't even close to the right shape, let alone in the right place. They're Chinese junk.

There are legitimate red bulbs. ECE R37 now contains provisions for a variety of them. WR5W (red W5W), RR5W and RR10W (red R5W and R10W), WR21W (red W21W), WR21/5W (red W21/5W), PR21W and PR21/5W (red P21W and P21/5W), etc. Except for the WR5W, these all have bases not interchangeable with the colorless or amber versions of the same bulbs, as required by R37. See for example here and here. BAW15d is the red-bulb variant of BAY15d; the index pins are clocked differently so the red and clear bulbs are not interchangeable. Osram made some ordinary-base red diadem P21Ws and P21/5Ws. Their p/n on the red diadem P21W is 7508LDR or 97508LDR; Candlepower got some in a couple years ago and may still have some left -- they are very costly.

 

[Hamilton Felix]

I agree about "legitimate." And I don't think the light output would be all that good. But if it gets you home without a ticket, after you crack a lens in the brush or in a parking lot, it might be good to have.

I'm tickled pink that I got to see my kids last night (one stationed in CA and one living in IA, haven't talked to me much since my divorce) right here in WA, along with my newest grandson. But when Megan left, driving ex-wife's car, I saw the left tail light broken out, lots of white light from both the brake/tail and the signal. I called her cell right away and told her. Apparently her mother knows but hasn't fixed it. I suggested at least some amber bulbs until she can get to a shop and replace that light (there's too much gone to really cover with red plastic and tape as we sometimes see). With a couple hundred miles of driving yet to do, I wonder if she'll make it back to Seattle without a ticket. This is exactly the situation where the colored bulbs -- legitimate or not, just so they light up -- might be worth having in the spares kit.

Naturally, I'd go for the best clear bulb available, as soon as I got home and got the lamp repaired. I only suggest the "truck stop specials" as a field expedient to avoid having one's hard-earned money taken by the State's armed & armored Revenue Collectors. Besides, dazzling other drivers with white light from the rear of a vehicle really is a Bad Thing, the law against it was written for a reason.