5 ms·

This development was discussed on HN about 3 days ago. On that thread I commented that a merit of the incandescent is its continuous output spectrum. The newe

by jrapdx3 11y ago

This development was discussed on HN about 3 days ago. On that thread I commented that a merit of the incandescent is its continuous output spectrum. The newer lamp technologies produce discontinuous spectral output, CFL having prominent green, and LED blue emissions. The difference is reflected in the CRI (Color Rendering Index) where 100 represents natural daylight. Incandescent lamps are generally very close to 100, but most fluorescent and LED sources are much lower, 90 or less. CRI is crucially important in the visual arts (museum/gallery lighting, photography, etc.) and other industries (color matching). There are fluorescent and recently LED lamps that have high CRI ratings. These are relatively expensive items different from the "bulbs" sold at the hardware store. For the future, "remote phosphor" LED lamps look promising, though likely there will be a market for improved incandescents as described in the article. Looks like advancements in LED, and now incandescent, technology could produce lamps that provide the best of both worlds: high CRI along with significantly extended durability.

darkmighty 11y ago
Note that due to how CRIs are calculated, you can have an arbitrarily bad color rendition even with any CRI <100 with discontinuous spectra: if your object reflects mostly on the bands where the spectrum is weak, it will appear black (or you could have a daylight e.g. red object appear e.g. blue or any other color). That's why incandescents are really the standard for color rendition.
ChuckMcM 11y ago
High CRI white LEDs have been a thing for a while though. While not completely continuous the high CRI GE "reveal" lights are pretty good [1]. [1] http://www.cnet.com/news/shining-a-light-on-high-cri-led-bulbs/ http://www.cnet.com/news/shining-a-light-on-high-cri-led-bul...
- amluto 11y ago
  I bought and returned a GE Reveal bulb. High CRI or not, it rendered colors terribly. Slate green turned purple. Bluish paint did something else nasty -- I forget exactly. It didn't look at all like incandescents, daylight, or other LEDs. We returned it and tried a high CRI Cree lamp. It looked normal.
  - ChuckMcM 11y ago
    Interesting, we've got a mix, The recent ones we put in are all Cree, but I have some of the Reveal ones in my workshop (with the Hue bulbs I got). If you could point me at an image of something with the kind of green you're talking about I'd love to try it under the Reveals I've got.
    - amluto 11y ago
      A literal piece of green slate. The Reveal in question was IIRC a 6" can downlight -- the kind that replaces the entire can trim.
jacobolus 11y ago
Note that by definition incandescent bulbs have a CRI of 100. The CRI is calculated by looking at the colors reflected by a particular set of 14 paint chips under the lamp being analyzed, and comparing it to either illuminant D65 (representing daylight) or to an incandescent bulb, depending on the lamp’s color temperature. The color from the paint chips undergo an outdated type of chromatic adaptation transform, and are then compared to the colors under the reference illuminant, using colorimetric distance in the outdated 1964 CIEUVW color space. To find the final CRI take the arithmetic mean of all the distances, scale it, and subtract from 100. Most of the choices in this process are somewhat arbitrary. CRI numbers are an okay first approximation to judge how much a particular lamp will muck with color relationships, but when you get to the precise details it gets pretty arbitrary, and the spec is heavily gamed by lighting vendors, because it’s one of the main values they report. Take CRI numbers with a big pinch of salt, and try looking directly at a chart of emission spectrum if you can, or ideally get a bulb and try looking at various objects under it for better understanding.
- bettercri 11y ago
  I've studied lighting tech on and off since getting into planted aquariums in 2006 and remember that some researchers at Philips also lamented the issues with CRI as a metric of light quality and presented their own system which I remember as being a color wheel with a lot of (possibly 100+) marked points. For each point, they'd present a vector as the difference from "actual" (as represented by the appearance in midday sun on a clear day) for a light source, so you could easily see how much a particular light skewed particular colors with fairly fine granularity. I neglected to save the source and haven't been able to find it in subsequent searchings though.
tempestn 11y ago
I don't know what you consider high, but FYI Cree has some relatively new bulbs that you can buy for under $10 at Home Depot with a CRI of 93 [1]. I've found Cree bulbs to be excellent in general. Tested a bunch of brands, and my house is full of these now. [1]: http://www.homedepot.com/p/Cree-TW-Series-60W-Equivalent-Soft-White-2700K-A19-Dimmable-LED-Light-Bulb-BA19-08027OMN-12DE26-2U100/205551228 http://www.homedepot.com/p/Cree-TW-Series-60W-Equivalent-Sof...

by jrapdx3 11y ago

darkmighty 11y ago

Note that due to how CRIs are calculated, you can have an arbitrarily bad color rendition even with any CRI <100 with discontinuous spectra: if your object reflects mostly on the bands where the spectrum is weak, it will appear black (or you could have a daylight e.g. red object appear e.g. blue or any other color). That's why incandescents are really the standard for color rendition.

ChuckMcM 11y ago

High CRI white LEDs have been a thing for a while though. While not completely continuous the high CRI GE "reveal" lights are pretty good [1]. [1] http://www.cnet.com/news/shining-a-light-on-high-cri-led-bulbs/ http://www.cnet.com/news/shining-a-light-on-high-cri-led-bul...

amluto 11y ago
I bought and returned a GE Reveal bulb. High CRI or not, it rendered colors terribly. Slate green turned purple. Bluish paint did something else nasty -- I forget exactly. It didn't look at all like incandescents, daylight, or other LEDs. We returned it and tried a high CRI Cree lamp. It looked normal.
- ChuckMcM 11y ago
  Interesting, we've got a mix, The recent ones we put in are all Cree, but I have some of the Reveal ones in my workshop (with the Hue bulbs I got). If you could point me at an image of something with the kind of green you're talking about I'd love to try it under the Reveals I've got.
  - amluto 11y ago
    A literal piece of green slate. The Reveal in question was IIRC a 6" can downlight -- the kind that replaces the entire can trim.

jacobolus 11y ago

Note that by definition incandescent bulbs have a CRI of 100. The CRI is calculated by looking at the colors reflected by a particular set of 14 paint chips under the lamp being analyzed, and comparing it to either illuminant D65 (representing daylight) or to an incandescent bulb, depending on the lamp’s color temperature. The color from the paint chips undergo an outdated type of chromatic adaptation transform, and are then compared to the colors under the reference illuminant, using colorimetric distance in the outdated 1964 CIEUVW color space. To find the final CRI take the arithmetic mean of all the distances, scale it, and subtract from 100. Most of the choices in this process are somewhat arbitrary. CRI numbers are an okay first approximation to judge how much a particular lamp will muck with color relationships, but when you get to the precise details it gets pretty arbitrary, and the spec is heavily gamed by lighting vendors, because it’s one of the main values they report. Take CRI numbers with a big pinch of salt, and try looking directly at a chart of emission spectrum if you can, or ideally get a bulb and try looking at various objects under it for better understanding.

bettercri 11y ago
I've studied lighting tech on and off since getting into planted aquariums in 2006 and remember that some researchers at Philips also lamented the issues with CRI as a metric of light quality and presented their own system which I remember as being a color wheel with a lot of (possibly 100+) marked points. For each point, they'd present a vector as the difference from "actual" (as represented by the appearance in midday sun on a clear day) for a light source, so you could easily see how much a particular light skewed particular colors with fairly fine granularity. I neglected to save the source and haven't been able to find it in subsequent searchings though.

tempestn 11y ago

I don't know what you consider high, but FYI Cree has some relatively new bulbs that you can buy for under $10 at Home Depot with a CRI of 93 [1]. I've found Cree bulbs to be excellent in general. Tested a bunch of brands, and my house is full of these now. [1]: http://www.homedepot.com/p/Cree-TW-Series-60W-Equivalent-Soft-White-2700K-A19-Dimmable-LED-Light-Bulb-BA19-08027OMN-12DE26-2U100/205551228 http://www.homedepot.com/p/Cree-TW-Series-60W-Equivalent-Sof...