Incandescent bulbs have a blackbody spectrum, usually somewhat redder than the sun’s (which is also close to blackbody radiation, modulo a few absorption lines). White LEDs have a much spikier spectrum, usually with two to maybe a half-dozen peaks at different wavelengths, which come from the band gaps of their component diodes (a “single” white LED usually includes two to four) or from the fluorescent qualities of phosphor coatings on them. High-quality LED bulbs use a variety of methods to tune the locations of these peaks and their relative intensities such that they’re visually close to sun or incandescent light; lower-quality ones tend to have them in weird places dictated by availability or ease of manufacture, which gives their light odd visual qualities and leads to poor color rendering. There are also tradeoffs involving the number of emitting diodes per unit. Information theory considerations mean that colors are never going to have quite the same fidelity under LED lights that they would under incandescent, but some can get damn close.
The same’s true in varying degrees for most other non-incandescent lights. The most extreme example in common use is probably low-pressure sodium lamps (those intense yellow-orange streetlights), which emit almost exclusively at two very close wavelengths, 589.0 and 589.6 nm.
The most extreme example in common use is probably low-pressure sodium lamps (those intense yellow-orange streetlights), which emit almost exclusively at two very close wavelengths, 589.0 and 589.6 nm.
Yep—if you take photographs under these lights (e.g. night street scenes), you essentially get tinted monochrome photographs. Under an almost-single-wavelength source of light there are no colors, only illumination intensities.
Incandescent bulbs have a blackbody spectrum, usually somewhat redder than the sun’s (which is also close to blackbody radiation, modulo a few absorption lines). White LEDs have a much spikier spectrum, usually with two to maybe a half-dozen peaks at different wavelengths, which come from the band gaps of their component diodes (a “single” white LED usually includes two to four) or from the fluorescent qualities of phosphor coatings on them. High-quality LED bulbs use a variety of methods to tune the locations of these peaks and their relative intensities such that they’re visually close to sun or incandescent light; lower-quality ones tend to have them in weird places dictated by availability or ease of manufacture, which gives their light odd visual qualities and leads to poor color rendering. There are also tradeoffs involving the number of emitting diodes per unit. Information theory considerations mean that colors are never going to have quite the same fidelity under LED lights that they would under incandescent, but some can get damn close.
The same’s true in varying degrees for most other non-incandescent lights. The most extreme example in common use is probably low-pressure sodium lamps (those intense yellow-orange streetlights), which emit almost exclusively at two very close wavelengths, 589.0 and 589.6 nm.
Yep—if you take photographs under these lights (e.g. night street scenes), you essentially get tinted monochrome photographs. Under an almost-single-wavelength source of light there are no colors, only illumination intensities.