The Light Bulb Database

No bulb has a health rating, so I measure the parts that matter for how light looks and how it affects the body clock: color rendering, how close the spectrum is to natural light, and the evening body-clock signal. Of the 86 white bulbs I measured, 38 have a CRI Re of 95 or higher and 16 are within 10% of natural light by spectrum.

I compare every spectrum with natural light at the same color temperature and report the average gap (ASD, lower is closer). 16 of 86 bulbs are within 10%, the "very close" tier; 30 are more than 25% off. Sort by "Closest to natural light" above.

"Full spectrum" has no standard definition, and color temperature only describes the color of the light, not how complete the spectrum is. Among the 27 bulbs at 4500K or cooler that I measured, the gap from natural light ranges from 8% to 26%: same color temperature, very different spectra.

On color quality, the average LED is. The 8 incandescent and halogen bulbs I measured have a median CRI Re of 98, against 92 for the 78 LEDs. The best LEDs match them: 30 LEDs reach CRI Re 95 or higher.

The warmer the light, the weaker the signal to the body clock. Median melanopic DER, the body-clock signal relative to daylight, by color: Amber: 12% of daylight; Warm white: 46% of daylight; Neutral white: 73% of daylight; Cool white: 88% of daylight. Amber bulbs send the weakest signal.

Not vitamin D: that needs UVB (290 to 315 nm), which household bulbs do not emit (NIH). For SAD, what matters is how much light reaches your eyes, not the spectrum. For measured light at 1 ft, see the SAD lamp database.