TheSamba.com :: View topic - LED color to use...red or white...for brake lights?

Sun Apr 04, 2010 1:40 pm

When changing out the bulbs in the brake lights to LEDs, should a red or white LED emitter be used? I'm guessing white since the brake lens is red and the bulbs output white. Would using red make the light more red, intense, or ??? Just wanna make sure.

P.S. I don't care about opinions of incandescent vs LED, light dispersion, pro vs con, yes or no, etc. That's been covered ad nauseum.

Sun Apr 04, 2010 1:46 pm

Air_Cooled_Nut wrote: When changing out the bulbs in the brake lights to LEDs, should a red or white LED emitter be used? I'm guessing white since the brake lens is red and the bulbs output white. Would using red make the light more red, intense, or ??? Just wanna make sure.

P.S. I don't care about opinions of incandescent vs LED, light dispersion, pro vs con, yes or no, etc. That's been covered ad nauseum.

Very well, you won't get my opinion, you can draw your own and report back your success or lack thereof.

However certainly *red* LED's are more suitable than white. More of the total output of the LED will make it through the lens.

Sun Apr 04, 2010 2:29 pm

Whatever is the brightest/most output

Sun Apr 04, 2010 2:31 pm

What he said. Red is more efficient in terms of light output vs power consumed. In other words, red should be brighter.

Sun Apr 04, 2010 3:11 pm

I used Red if you go with all 4 LEDs your dash blinker indicator will stop working FYI.

Sun Apr 04, 2010 3:22 pm

The trucks I work on all have red LED assemblies, as stock.
They light up VERY well, vs. an incandescent lamp....... oops, there I go again....... 8)

Sun Apr 04, 2010 4:26 pm

Red for sure as white will shine white through your red lens. I have changed all four signals and brake/tail lights in my bus, also did my car and truck too. I always use 360 degree leds so that they light up the bucket too and make you more visible. To make your flasher work with leds in all of the signals you will either need an led specific flasher or some load equalizers to put extra load on the circuit to trip you stock flasher.

Sun Apr 04, 2010 4:51 pm

jonnie5 wrote: To make your flasher work with leds in all of the signals you will either need an led specific flasher or some load equalizers to put extra load on the circuit to trip you stock flasher.

you could do it that way or with 2 green LED's 2 470ohm 1/2w 5% resistors a soldering iron and a few feet of wire you can rig up some independent blinkers. :wink:

Sun Apr 04, 2010 7:08 pm

Red it is, thanks volks.

BTW, the conversion isn't for my Bus and, IMHO, even though I clearly stated it was for a brake light, LED blinkers are unnecessary, bulbs are fine for that function.

Sun Apr 04, 2010 9:36 pm

dont use led tail lamps. the are a directional lighting source. have you ever noticed if you arent looking directly at one they arent very bright? this is due to the design. i would run a nice new incandecent bulb.

Sun Apr 04, 2010 10:03 pm

I would go with white. Here is why. White light has all colors. When you see red light coming out of that lens it is because the red in the plastic is stopping any color of a different wavelength and that color red is all that is getting through. If you for example put a green light in there you would not see it hardly at all. There are many red colors. You cannot be sure your red LED will be the same wavelength as the red lens, and with sunlight the red lens may bleach towards the blue side because of UV. If you use the white LED, no matter what color the red lens is or becomes, you have a better chance maximum light will get through.

The other alternative would be to buy one small LED of each and test both next to each other to see which is brightest.

Mon Apr 05, 2010 6:33 am

jonnie5 wrote: Red for sure as white will shine white through your red lens. I have changed all four signals and brake/tail lights in my bus, also did my car and truck too. I always use 360 degree leds so that they light up the bucket too and make you more visible. To make your flasher work with leds in all of the signals you will either need an led specific flasher or some load equalizers to put extra load on the circuit to trip you stock flasher.

Actually they won't. Your regular incandescents are white...and they don't shine "white" through the red lens. The red lens is actually a filter. It filters all of the visible spectrim out except the red....thats why you see red instead of ornage, yellow, blue, purple etc....which are all colors/wavelengths of light that are actually included in the visible white light that an incandescent bulb creates.

This is also why....as someone else previously commented......with an LED, you get better intensity by using a red LED as compared to a white LED. LED's tend to have a narrower spectral range. Not quite single spectrum like colimated light.....but narrower than multi-spectrum incandescent.
So...if your LED is say....only 5 watts....and you want red, if you use a red LED....you might get close to a total of five watts red output...which goes right through the red filter of the red lens......as compared to a white LED which may only produce a smaller fraction of red light as part of the total white spectrum.

The reason why a five watt incandescent does not have this problem is because though it may produce the same total wattage....it produces a higher level of "lumins". In short ...its more intense.

This is about the question of wattage.
About the question of actual color......
SGKent has a very correct point.....

Quote: I would go with white. Here is why. White light has all colors. When you see red light coming out of that lens it is because the red in the plastic is stopping any color of a different wavelength and that color red is all that is getting through. If you for example put a green light in there you would not see it hardly at all. There are many red colors. You cannot be sure your red LED will be the same wavelength as the red lens, and with sunlight the red lens may bleach towards the blue side because of UV. If you use the white LED, no matter what color the red lens is or becomes, you have a better chance maximum light will get through.

In reality....the very lowest maintenance way to work...would be to go to a higher wattage full spectrum white LED

Mon Apr 05, 2010 9:02 am

Quote: White light has all colors.
When speaking of sunlight or tungsten based light, this is true. For gas discharge, fluorescent, or LED, it's not. If you've ever tried to judge a car's color in a parking lot at night, you've experienced this problem.

White LEDs are of two types: one generates white by causing a 'white' phosphor to glow by bombarding it with ultraviolet light generated by the LED. The other is a dual LED in a single package where one LED die is blue and the other LED die is yellow. Both of these methods fool the eye into seeing 'white' light. In actuality, there are holes in both of their spectrums. {Same phenomenon applies to neon, fluorescent, and HID lamps. This is why they have a CRI (Color Rendering Index) rating.}

Point is, if the color of your lens happens to not transmit all of the color components being emitted by the LED, then much brightness will be lost - regardless of whether the LED is red or white. This is a big problem in the sign business where plastic faces are put over LED light sources.

Only practical way to find out is to spend the bucks, buy a bulb, and try it out.

Mon Apr 05, 2010 10:25 am

telford dorr wrote: Quote: White light has all colors.
When speaking of sunlight or tungsten based light, this is true. For gas discharge, fluorescent, or LED, it's not. If you've ever tried to judge a car's color in a parking lot at night, you've experienced this problem.

White LEDs are of two types: one generates white by causing a 'white' phosphor to glow by bombarding it with ultraviolet light generated by the LED. The other is a dual LED in a single package where one LED die is blue and the other LED die is yellow. Both of these methods fool the eye into seeing 'white' light. In actuality, there are holes in both of their spectrums. {Same phenomenon applies to neon, fluorescent, and HID lamps. This is why they have a CRI (Color Rendering Index) rating.}

Point is, if the color of your lens happens to not transmit all of the color components being emitted by the LED, then much brightness will be lost - regardless of whether the LED is red or white. This is a big problem in the sign business where plastic faces are put over LED light sources.

Only practical way to find out is to spend the bucks, buy a bulb, and try it out.

I actually teach color theory for a living. ...and you are incorrect.....partially......gas discharge flourescent (pick your shade of white if you please)...and white LED's.....though they have a much more narrrow spectrum because of how they make their light.....also have the same multi-spectral split of white light. They just are not as contaminated by as broad of a range of spectrum.

For instance both LED's and gas flourescents have very low levels of infrared (LED's have almost none). Unless LED's are "doped" to do so......they also put out very little UV.
Flouerescent actually puts out a respectable amount of UV as you get above 4200K color temp. 6500K lamps with CRI above 88 actually have quite a bit of UV.

In either case.....if you see white light...then it is a composite spectrum of white light.....period.
There is no "singular" white light spectrum in this universe. In fact there is np white light at all.
This is because visual light color (that which is made of transmitted light)....is "additive".....it is created out of multiple spectra.

If you manufacture an LED that produces a VISIBLE white light....even though that white light might be very narrow in the spctra contained within it......it will still split out to multiple spectra with a prism.

You are confusing the fact you are using either UV bombarded doped LED or dual spectrum....with the idea that white light is not being created.

When in fact....any of those ingredients can and will emit multiple spectra and in fact....they are additive. In fact.....for example.....white on a monitor screen is made up of "relatively" equal parts of Red,green and blue.
If you SEE white colored light...no matter what produces it....it produces a fully prism splittable spectrum. You will see the rainbow either way. Ray

Mon Apr 05, 2010 4:44 pm

I have a degree in photography and love physics so I agree w/Ray, there's no such thing as a single color "white" like there is "blue" or "red".

Red one is on order. If it doesn't seem bright enough to me I'll get a white unit

But let's not get into an argument over color semantics, m'kay?

Mon Apr 05, 2010 7:05 pm

You techie volks blow my mind! I'm on absolute pins and needles to find out your results!! By the by, on my old 71 i have just the one bulb to perform both functions ,and rather dimly i might add, but i have recently become aware of a euro style 2 bulb housing that can be swapped in which includes a yellow blinker section. i have searched fruitlessly for a thread or a link to where one might find such an item. I'd be etrnally grateful if anyone has a link to share.... (not to hijack or anything) 8) 8)

Mon Apr 05, 2010 7:14 pm

there actually is a lot of talent here on TheSamba of many different trades.

Mon Apr 05, 2010 7:19 pm

SGKent wrote: there actually is a lot of talent here on TheSamba of many different trades.
:wink: That's why I asked here.

Tue Apr 06, 2010 9:35 am

Quote: If you SEE white colored light...no matter what produces it....it produces a fully prism splittable spectrum. You will see the rainbow either way.
Ray,

Understand all that. My point is that, with fluorescent and LED sources, the spectrum that the prism will split out will have significant 'holes', or gaps in it. The eye dismisses these discontinuities, unless said 'white' light is passed through a filter which attenuates a large portion of the spectrum, leaving a situation where the spectral holes in the remaining transmitted light become significant. The results may not appear as one might hope. More specifically, placing a 'yellow-blue' type 'white' LED behind a red lens will probably not yield the same light output that, say, a normal equivalent tungsten (continuous spectrum) bulb would. Thus, unless one has a spectrometer or other measuring equipment available to analyze the LED's spectral content and the lens' transmission spectrum, then 'cut and try' is the only practical method of determination, and one must be prepared for unexpected results.

Sat Apr 24, 2010 8:08 am

I ended up using this for my rear tail light on my Ducati (1157):
http://www.superbrightleds.com/cgi-bin/store/index...-x18-T.htm

On the web site it states that the LED unit color should match the lens it's going into (red lens, use red LED). The guys on the Ducati forum I'm on confirmed and basically echoed what was said here, that the "white light" from LEDs is too narrow of a spectrum.

Install:
http://www.aircoolednut.com/cmgallery/thumbnails.php?album=126

I haven't compared my LED side-by-side another Sport Classic but from general observation the parking light intensity is the same but with more light observable to the sides as well. The brake light is, without a doubt, way more brighter than the stock 1157 incandescent bulb and throws more observable light all around i.e., sides are as bright as the rear.

I wasn't holding my breath that the LED unit would work but was pleasantly surprised that it did work. The 360 configuration does help and I think if placed in the more confined Bus tail light one would not be disappointed at all with their performance.