4 ms·

Color temperature isn't the only thing, CRI is important too (though less so). It's hard to find CRI specs on most bulbs, nobody mentions it unless they have a

by mark-r 10y ago

Color temperature isn't the only thing, CRI is important too (though less so). It's hard to find CRI specs on most bulbs, nobody mentions it unless they have a really good number to brag about (90+). One thing never mentioned is that LED color temperature will vary over time. It's a two-part system with complementary colors, the LED itself is blue and it's coated or surrounded with a yellow phosphor. The phosphor will dim eventually. I've never seen a LED bulb that was so slow to light up that I noticed it, unlike some fluorescents that are really atrocious. I've already given up on fluorescents, if only for the hassle of recycling them due to the mercury content.

tempestn 10y ago
Normally when people complain of led bulbs being slow to turn on, it's actually the dimmer at fault. Most dimmer switches have only two wires, and so charge their caps through the bulb. Since LEDs draw far less current, this takes longer, and so the bulb takes longer to appear on.
- danielweber 10y ago
  I have some stairways I must light up and they need to light up instantly for safety reasons. I make sure one of the bulbs in the fixture is incandescent, and CFL/LED the rest.
  - tempestn 10y ago
    You can also not use a dimmer, or use a (quality) dimmer intended for LED bulbs. (Many dimmers supposedly for LEDs will still not turn on instantly.)
    - danielweber 10y ago
      I have no dimmers at all in my house.
      - tempestn 10y ago
        Bizarre that the LEDs would have a delay then, or that including an incandescent would make any difference in that delay. (Or are you saying it doesn't make a difference in how quickly the leds turn on, but it itself turns on faster? I guess if they're cheap ones with poorly tuned internal rectifiers that could be the case.)
        danielweber 10y ago
        I need some light immediately, and the incandescent gives me some light immediately.
deleted 10y ago
[deleted]
rconti 10y ago
My Cree Type A LED replacement bulbs are over 90 CRI. Incidentally, is CRI a totally bullshit measurement, or does it mean something? I find it oddly coincidental that an incandescent supposedly has a CRI of 100 and matches daylight. How is this possible for such an old tech? Did they just get really lucky with the first lightbulb? Or have the gases and filament material improved over time to bring CRI up to 100? I have a hard time believing CRI was the ultimate goal of incandescent development, but I could be wrong.
- jacobolus 10y ago
  CRI measures how close (using a terrible metric) oranger lamps get to a black body radiator, or how close bluer lamps get to an approximation for daylight from the 60s, which each have a CRI of 100 by definition. Incandescent bulbs are a black body radiator, so unless you put some kind of filter in front, they’ll have a CRI of 100. It’s not a 0–100 scale though. 100 is an arbitrarily selected number. There are reasons to be dissatisfied with the light produced by LEDs and fluorescent lamps, but CRI is only very marginally useful. Better is to look at the spectral power distribution, and try to find lamps with a broad emission spectrum and no sharp spikes. For nighttime lighting, try to avoid sources with much emission at wavelengths below 500 nm, because these knock out night vision and disrupt sleep cycles.
  - giorgosts 10y ago
    CRI measures how natural the objects' colors appear under an artificial light source against the objects colors under a natural light source (standardized daylight). The color temperature and luminosity of natural light sources varies tremendously during the course of the day or in different parts of the world, yet the objects colors remain consistent. This is a property of the human vision called chromatic adaptation. https://en.wikipedia.org/wiki/Chromatic_adaptation https://en.wikipedia.org/wiki/Chromatic_adaptation Sources which emit a continuous spectrum have better CRI than tri-color sources, especially on artificially colored objects (dyed/pigmented) due to metamerism. https://en.wikipedia.org/wiki/Metamerism_(color) https://en.wikipedia.org/wiki/Metamerism_(color)
metafunctor 10y ago
Yep, the spectrum of light emitted is what matters. A histogram or spectrum intensity curve printed on the cardboard package would be ideal. Sadly, I've never actually seen that in consumer grade stuff. I've found that most LED bulbs you can find in supermarkets are really quite bad in this respect. For my home office, I got something called "True-Light" E27 bulbs. The specs are 12W, 5500K, 920lm, CRI 94. They emit a passable bright, white light. My favourite light source are still E11 halogens. Just pepper the ceiling with them, add dimmers, and hope it doesn't heat up the room too much…

by mark-r 10y ago

tempestn 10y ago

Normally when people complain of led bulbs being slow to turn on, it's actually the dimmer at fault. Most dimmer switches have only two wires, and so charge their caps through the bulb. Since LEDs draw far less current, this takes longer, and so the bulb takes longer to appear on.

danielweber 10y ago
I have some stairways I must light up and they need to light up instantly for safety reasons. I make sure one of the bulbs in the fixture is incandescent, and CFL/LED the rest.
- tempestn 10y ago
  You can also not use a dimmer, or use a (quality) dimmer intended for LED bulbs. (Many dimmers supposedly for LEDs will still not turn on instantly.)
  - danielweber 10y ago
    I have no dimmers at all in my house.
    - tempestn 10y ago
      Bizarre that the LEDs would have a delay then, or that including an incandescent would make any difference in that delay. (Or are you saying it doesn't make a difference in how quickly the leds turn on, but it itself turns on faster? I guess if they're cheap ones with poorly tuned internal rectifiers that could be the case.)
      - danielweber 10y ago
        I need some light immediately, and the incandescent gives me some light immediately.

deleted 10y ago

[deleted]

rconti 10y ago

My Cree Type A LED replacement bulbs are over 90 CRI. Incidentally, is CRI a totally bullshit measurement, or does it mean something? I find it oddly coincidental that an incandescent supposedly has a CRI of 100 and matches daylight. How is this possible for such an old tech? Did they just get really lucky with the first lightbulb? Or have the gases and filament material improved over time to bring CRI up to 100? I have a hard time believing CRI was the ultimate goal of incandescent development, but I could be wrong.

jacobolus 10y ago
CRI measures how close (using a terrible metric) oranger lamps get to a black body radiator, or how close bluer lamps get to an approximation for daylight from the 60s, which each have a CRI of 100 by definition. Incandescent bulbs are a black body radiator, so unless you put some kind of filter in front, they’ll have a CRI of 100. It’s not a 0–100 scale though. 100 is an arbitrarily selected number. There are reasons to be dissatisfied with the light produced by LEDs and fluorescent lamps, but CRI is only very marginally useful. Better is to look at the spectral power distribution, and try to find lamps with a broad emission spectrum and no sharp spikes. For nighttime lighting, try to avoid sources with much emission at wavelengths below 500 nm, because these knock out night vision and disrupt sleep cycles.
- giorgosts 10y ago
  CRI measures how natural the objects' colors appear under an artificial light source against the objects colors under a natural light source (standardized daylight). The color temperature and luminosity of natural light sources varies tremendously during the course of the day or in different parts of the world, yet the objects colors remain consistent. This is a property of the human vision called chromatic adaptation. https://en.wikipedia.org/wiki/Chromatic_adaptation https://en.wikipedia.org/wiki/Chromatic_adaptation Sources which emit a continuous spectrum have better CRI than tri-color sources, especially on artificially colored objects (dyed/pigmented) due to metamerism. https://en.wikipedia.org/wiki/Metamerism_(color) https://en.wikipedia.org/wiki/Metamerism_(color)

metafunctor 10y ago

Yep, the spectrum of light emitted is what matters. A histogram or spectrum intensity curve printed on the cardboard package would be ideal. Sadly, I've never actually seen that in consumer grade stuff. I've found that most LED bulbs you can find in supermarkets are really quite bad in this respect. For my home office, I got something called "True-Light" E27 bulbs. The specs are 12W, 5500K, 920lm, CRI 94. They emit a passable bright, white light. My favourite light source are still E11 halogens. Just pepper the ceiling with them, add dimmers, and hope it doesn't heat up the room too much…