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Thread: streetlights with greenish-yellow tinged cast

  1. #1

    Default streetlights with greenish-yellow tinged cast

    I realise this has to do with fixed lighting, but thought it might be more appropriate to put it here.

    I recently saw the parking lot in front of a local strip mall installed some new LED street lighting. What's interesting about these LED street lights is they have an obvious yellow-green color cast to them. They're not all yellow-green in color, the light is kind of whitish too.

    The light has an interesting feel. It feels a little "softer" and warmer, like high pressure sodium street lamps, but still a little industrial and sickly, off-color.

    It's as if someone took some LED phosphor intended for 5000K and covered them over the dye with a thickness normally used for 3000K LEDs. And I am talking lower 70 CRI phosphor here, the type normally used for streetlamps.

    I got right under the lights too, because I know sometimes with these cheap LED streetlamps the exact color of the light can vary with the angle and if you're standing right under it the light will be whiter than it looks viewed from a distance, but that was not the case here, the color of the light was still the same standing right under it and looking up.

    I'm not sure exactly why these streetlamps were tinted, but could put forth a few guesses. It could have just been low quality. Perhaps this was an intentional strategy for maximum lumen output. With a greater portion of the blue light converted into yellow-green light through the phosphor, the lumen efficiency would have been raised (since the eye has several times higher sensitivity to green light than to blue light). Light quality probably wasn't seen as mattering so much since these were just replacing sodium streetlamps.
    Or maybe the lights were designed for reduced glare, by allowing less blue light through the phosphor. I could still see blue color objects under the light, but these blue colored objects seemed kind of dull in blue coloration.

    I think I kind of preferred these streetlamps over the regular 5000K streetlamps. It feels softer and less glaring. There were 5000K streetlamps lining the street right in front of the parking lot so I could see both side by side. The normal streetlamps seemed a light more bluish and magenta-tinted in comparison.

  2. #2

    Default Re: streetlights with greenish-yellow tinged cast

    Quote Originally Posted by JoakimFlorence View Post
    I realise this has to do with fixed lighting, but thought it might be more appropriate to put it here. I recently saw the parking lot in front of a local strip mall installed some new LED street lighting. What's interesting about these LED street lights is they have an obvious yellow-green color cast to them. They're not all yellow-green in color, the light is kind of whitish too. The light has an interesting feel. It feels a little "softer" and warmer, like high pressure sodium street lamps, but still a little industrial and sickly, off-color. It's as if someone took some LED phosphor intended for 5000K and covered them over the dye with a thickness normally used for 3000K LEDs. And I am talking lower 70 CRI phosphor here, the type normally used for streetlamps. I got right under the lights too, because I know sometimes with these cheap LED streetlamps the exact color of the light can vary with the angle and if you're standing right under it the light will be whiter than it looks viewed from a distance, but that was not the case here, the color of the light was still the same standing right under it and looking up. I'm not sure exactly why these streetlamps were tinted, but could put forth a few guesses. It could have just been low quality. Perhaps this was an intentional strategy for maximum lumen output. With a greater portion of the blue light converted into yellow-green light through the phosphor, the lumen efficiency would have been raised (since the eye has several times higher sensitivity to green light than to blue light). Light quality probably wasn't seen as mattering so much since these were just replacing sodium streetlamps. Or maybe the lights were designed for reduced glare, by allowing less blue light through the phosphor. I could still see blue color objects under the light, but these blue colored objects seemed kind of dull in blue coloration. I think I kind of preferred these streetlamps over the regular 5000K streetlamps. It feels softer and less glaring. There were 5000K streetlamps lining the street right in front of the parking lot so I could see both side by side. The normal streetlamps seemed a light more bluish and magenta-tinted in comparison.
    Maybe it's an effect similar to the Cree rainbows we see in flashlights. With older non LED types there was variance in tints and casts. I like some of the metal halide type lighting in use and they generally looked white but sometimes I would see some with slight green, blue, or even purplish casts.

  3. #3

    Default Re: streetlights with greenish-yellow tinged cast

    Quote Originally Posted by 18650 View Post
    With older non LED types there was variance in tints and casts.
    I think this goes beyond variance. It was either a fairly serious manufacturing design mistake, extreme carelessness (maybe low quality emitters from China) or it was intentional.
    Anyway, I hate the magenta cast of most LED lamps (especially prevalent in lower CRI ones it seems) so this makes me happy.

    Another plausible possibility off the top of my head, they could have used a low quality phosphor formulation that they knew would result in color shift over time, so they added extra phosphor to try to compensate for the color shift they expect to happen a few years from now. (Color shift is associated with lumen depreciation)
    Last edited by JoakimFlorence; 11-08-2018 at 03:56 PM.

  4. #4
    Flashaholic* FRITZHID's Avatar
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    Default Re: streetlights with greenish-yellow tinged cast

    We recently had some of the old sodium street lights replaced with LED in my very small town & MUCH to my surprise, they are VERY close to their sodium counterparts! I was shocked to see this.
    Idk if it was intentional or not but I believe a warm but more even spectrum light would have been better.
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