Värviesitusindeks

Värviesitusindeks, often abbreviated as CRI or Ra, is a quantitative measure of a light source's ability to reveal the colors of various objects faithfully compared to a natural light source. It is a scale from 0 to 100, where a CRI of 100 indicates that the light source renders colors identically to a natural light source, such as the sun. A lower CRI value suggests that the light source is less effective at accurately reproducing colors.

The CRI is determined by comparing the spectral power distribution of the light source in question to that of a reference illuminant. The reference illuminant is chosen to be spectrally similar to the light source being tested, and for most common applications, this reference is either a black-body radiator (for incandescent and halogen lamps) or a standard daylight illuminant. Specific color samples are illuminated by both the test source and the reference illuminant, and the differences in how their colors appear are measured. These differences are then averaged to produce a general CRI value.

Different applications have different CRI requirements. For general indoor lighting, a CRI of 80 or above is typically considered good. For applications where color accuracy is critical, such as in art galleries, retail displays, or healthcare settings, a CRI of 90 or higher is often preferred. While CRI is a widely used metric, it's important to note that it doesn't account for all aspects of color perception, and some sources with high CRI may still exhibit certain color rendering characteristics that are not ideal.