Which light source has the lowest CRI?

Which light source has the lowest CRI?

• A. High Pressure Sodium
• B. Incandescent
• C. LED
• D. Daylight

Answer: (A)

Color rendering index (CRI) measures how accurately a light source reveals colors compared with a reference light. A higher CRI means colors look more natural under that light. High Pressure Sodium has the lowest CRI because it emits light from a very narrow range of wavelengths—mostly a strong yellow-orange from sodium lines—so many colors can’t be distinguished accurately and appear distorted. This limited spectrum yields a CRI in the low range, much lower than incandescent lighting, daylight, or most LEDs, which have broader spectra and render colors more faithfully.

Color rendering index (CRI) measures how accurately a light source reveals colors compared with a reference light. A higher CRI means colors look more natural under that light. High Pressure Sodium has the lowest CRI because it emits light from a very narrow range of wavelengths—mostly a strong yellow-orange from sodium lines—so many colors can’t be distinguished accurately and appear distorted. This limited spectrum yields a CRI in the low range, much lower than incandescent lighting, daylight, or most LEDs, which have broader spectra and render colors more faithfully.