>>4248409So LED lamps have the following problem: Their spectral composition does not match what is considered standard white.
Basically: White LEDs are usually blue LEDs with some phosphorescent material in front of it. The blue light excites the phosphorescent material, which glows yellow or whatever. The geometry of the whole thing is set up in a way, that both colors mixes to something that looks white.
Standard white is a thermal spectrum, meaning it has only one component, which has no further structure, no peaks or notches. Thermal light sources are the sun, fire and traditional light bulbs. See this shitty illustration I made. X-axes are the wavelength.
Both spectra are perceived as white, the reason is that all three rods have a range of sensitivity, meaning if in that range of sensitivity the integrated light intensity (multiplied by some sensitivity curve) is the same for two colors, the color will appear the same for that type of rod. So the lack of mid-wavelength light in the LED light is counteracted by more low-wavelength light, so that the cone response is the same.
Now, you may say, it doesn't matter what the exact spectral composition is because we have only three types of cones, therefore all that matters is how these three cones perceive the color. If it is white, then who cares?
It's all about subtleties. Really, I'd say you really don't need to care if you don't care about subtleties. But here's what can happen (it won't, for the most part): You have the pigment with the absorption spectrum on the bottom. It has three notches. Let's say under standard light, the pigment is perfectly gray. Under the LED light however, more of the light contributing to the blue cone part of the spectrum will be absorbed (as the notch matches the peak of the LED), so the light will look yellowish.
