Wavelength to Color Converter (nm → sRGB)

The human eye barely sees wavelengths below ~420 nm or above ~700 nm — the long/short cone responses fall off rapidly. The conversion applies an intensity rolloff in those regions to match that perceptual fade, so a 'pure 380 nm' color is rendered as a dim violet rather than a vivid one.

It's a useful approximation, not a colorimetric reference. The piecewise function captures the hue progression of the visible spectrum well, but sRGB has a smaller gamut than the visible spectrum — many monochromatic colors (especially deep cyan/teal around 480–500 nm) physically cannot be reproduced on a screen. The shown color is the closest in-gamut approximation.

Dark gaps in the solar spectrum caused by elements in the Sun's atmosphere absorbing specific wavelengths. Joseph von Fraunhofer catalogued ~570 of them in 1814 using a prism, and labelled the strongest ones A–K. They're now the standard reference wavelengths for spectroscopy and stellar classification — the D lines at 589 nm, for example, are the same yellow you see from a sodium street lamp.

UV (below 380 nm) and IR (above 780 nm) are invisible to humans, so they're shown as black. The wavelength selector is capped to the visible range. For a UV blacklight glow, look at the 400–420 nm range — actual UV is below visibility.