Color rendering index
Videos
A color rendering index is a quantitative measure of the ability of a light source to reveal the colors of various objects faithfully in comparison with a natural or standard light source.
Emitted light spectrum determines the CRI of the lamp. An incandescent lamp (middle image) has a continuous spectrum and therefore a higher CRI than a fluorescent lamp (lower image). The top image shows the setup of the demonstration from above.
Sodium-vapor lamp
Videos
A sodium-vapor lamp is a gas-discharge lamp that uses sodium in an excited state to produce light at a characteristic wavelength near 589 nm.
Color rendering index
…of daylight, very close to that of a black body (incandescent lamps are effectively black bodies), dropping to negative values for some light sources. Low-pressure sodium lighting has a negative CRI; fluorescent lights range from about 50 for the basic types, up to about 98 for the best multi-phosphor type. Typical white-color…
Sodium street lights in Tuntorp, Sweden
An HPS lamp after turning off. The alumina material glows red because it is still hot.
Two Honda Fits under low-pressure sodium lamps. Both appear black, even though the car on the left is bright red, while the car on the right is actually black.
High-pressure sodium lamps (SON).