Stick with me here, I will explain some missing pieces about lighting quality: There are two commonly available ways to characterize the quality of artificial light. One is Correlated Color Temperature (CCT), the other is Color Rendering Index (CRI).
CCT is on the Kelvin scale; if you heat a piece of tungsten to 2700 degrees K it glows that nice warm yellow color given off by a standard voltage incandescent light bulb. At 5000 degrees K, you have a blue-white color which is more or less the color temperature of natural daylight (it can go much higher). 2700K just feels good to a lot of people for various reasons; light is a very psychologically charged issue. 5000K looks blue and cold when a light bulb makes it, but we actually have better visual acuity in this range and task lighting like shop lighting is great in this color temperature.
Paradoxically, the 2700K light is described as "warm" while the 5000K light is described as "cool", but it's all about that glowing hot metal color, so we just have to get used to the blue 5000 degrees Kelvin being called "cool". It's crazy. Try to find the actual CCT for any light rather than the silly names ("cool white"; WTH does that mean?) the companies give them.
Fluorescent lamps have been commonly available in CCTs of 2700, 3000, 3500, 4100, 5000 and ~6500K. If you look at the lighting on the ceiling in stores and offices you will often see different colors of lamps installed next to each other. "Warm" CCTs are more atmospheric, while "cool" CCTs are better for task lighting like reading printed materials and measurements. A lot of cheap shop lighting is 4100K. "Full spectrum" lamps are typically up around 6500K and have a high CRI, but we'll get to that. Full spectrum is a marketing ploy, not a good technical description.
CRI is based on an arbitrary scale where natural sunlight has a value of 100 at rendering colors accurately; 100 is as good as it gets. Remember daylight has a CCT of around 5000K? Paradoxically, an incandescing incandescent bulb does a pretty good job mimicking the full spectral energy distribution of the sun, so they have an assigned CRI of 100, with a CCT of around 2700K. But remember CRI and CCT are entirely independent of each other in artificial light sources.
All the other artificial light sources we have
fall short of incandescents in their CRI. Fluorescents and LEDs are available with CRIs in the mid-90's, which is actually pretty good; most people can't tell any difference. Higher CRI is always better, but we pay more for higher CRI, and it is worth some extra money for the light quality if we are doing task lighting or spending a lot of time under it. Residential fluorescents and LEDs are available with CRIs under 60, which is terrible. CRIs at 80-90 aren't bad, and probably fine for ambient lighting. Many of the cheap fluorescents we labored under for years have CRIs in the 70s.
It is often hard to find CRI numbers on the packaging, so we have to look for them on the insert or ask the seller to give us the specs for the lamp. It often seems like if the manufacturer is not proud of the CRI, it will be hard to find.
Just to add to the fun, IESNA is introducing a new TM-30-15 standard where the CRI metric will be replaced by two separate metrics and a graphic: CRI will be replaced by Rf, but the numbers will be pretty similar. Fidelity index (Rf), which is basically an updated CRI between 8 and 99.
One big question here is: What kind of light should we be using? Natural sunlight is best, and essential for our health. Getting out in the sun daily is very important, just don't get a sunburn. Check out the cutting edge health and fitness search engine at
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LED lighting is so incredibly energy efficient and long-lived it has literally changed the way we think about the costs and environmental consequences of good lighting. Incandescent lighting is 90% heat and 10% light and burns out quickly, so it wastes most of the energy we pay for, but based on my reading it is probably the healthiest artificial light to spend a lot of time under, especially at night. Avoiding blue light sources like computer screens at night can help us sleep better. Free apps like IRIS are available to change the CCT of our computer screen based on the time of day. Does it make sense to use incandescent task lighting in winter when the daylight is short and we are inside using the heat a lot, and use LEDs the brighter half of the year, April to September, when the AC may be on? I try to spend more time outside during daylight and use 2700K LEDs except in the shop/garage. Certainly the more we can use natural daylight the better for us and our Earth.