[Tonkabot]

Don't you want white light LEDs for use in fixtures that have colored lenses? It seems to me that I recall from reading somewhere else that red bulbs behind red lenses doesn't work as well for brightness. Maybe I am mistaken, but that is what I remember about this.

It shouldn't be a problem. A red LED behind a red lens should put out as much light as a red LED behind a clear lens.
The lens will cut down on all light transmission a little - if it is a red lens it is a band pass filter for red light, and ALL (except for the losses of the lens itself - present if clear or red) of the light from a red LED will pass. having a lens (red OR clear) will cutdown a little bit of light, but better than having your LED's out in the elements.


Also, I think an H4 3 prong bulb has both high and low beams, don't we want just a H1 (low beam?) bulb? Does the tractor have a high beam switch? does it just energize both the high and low elements at once?

 

[Tonkabot]

It's not the lens, it's the LED. A red LED produces way way less lumens than a comparable white LED of the same size and form. Putting a white LED in the red taillight will produce much brighter red light out the lens than a red LED behind the red lens. Also, the red lens is NOT bandpass. There is significant loss passing through it. A red LED alone without the lens will be much brighter than a red LED behind a red lens.

Okay, I believe you about the red lens adding significant loss to a red LED. Of course it also has significant loss with a white LED - actually a much greater loss as it will block blue, green and yellow (and everything in between).

One thing to know about White LED's is that there is really no such thing. They are Blue LED's with phosphers. The blue light excite the phosphers, which re-emit the energy in all colors of the spectrum.

Comparing white LED lumen output to a red LED lumen output and then comparing what comes through a red lens is not really fair. If you start with a red LED that has 100 Lumen and a white LED that has 100 lumen, After the a red lens the RED LED will appear MUCH brighter. Not fair to start with a 1000 Lumen white and compare to 100 lumen red.

 

[Tonkabot]

Digi-key has about 50,000 different LED types available. I live in a world where I pick the LED I want with the characteristics I like from that group. You are comparing from the handful of different LED bulbs that someone has designed and manufactured to replace a clear incandescent bulb. A designer could choose to design a red 1156 replacement bulb, and if he chooses, that red bulb could be insanely brighter than a white bulb. It would have much less waste heat than a white LED used inside the red lens.

Here is the LED place that has a wide selection: various 1156 bulbs
You will find they have 1156 bulbs with 3 different white color temperatures, or red or amber, listed at 325 lumens (among others). I suggest you try buying one of these in red, amber, and white. You'll find the red is brighter than the white when behind a red lens (if they are not lying about the exact lumen output they advertise). It's physics.

(disclaimer: I have bought from the superbrightled web site several times, and have always been happy with what they sold me)

It's a fair comparison because none of the products on the market are like that. A 1156 replacement LED bulb in red is the same size and form of a 1156 replacement LED bulb in white. The white 1156 LED produces significantly more lumens than the 1156 red LED. There is no such thing as a replacement LED bulb for these things where the same lumen output exists across the color options. The white bulb you buy for that thing will be way brighter than the red bulb. Therefore putting the white one behind the red lens will produce way more red light for you.

This is why I have white 1156 and 1157 LED replacements in both the red and the amber lights. The end result is way brighter red and amber light than had I used Amber and red LEDs.

 

[Tonkabot]

Okay. I should have looked at the full specs to see that they were lying with the lumen output.

You are right with what is available. I'm just too literal minded - if you really have a 100 lumen red and a 100 lumen white, the red will be brighter behind the red lens [than a same lumen white behind the red lens]. physics.

It wouldn't occur to me that I should compare a 325 lumen white to a 45 lumen red and then say the white is brighter.