Typical Values
| Light source | CCT (K) | CRI |
|---|---|---|
| Low-pressure sodium (LPS/SOX) | 1800 | ~5 |
| Clear mercury-vapor | 6410 | 17 |
| High-pressure sodium (HPS/SON) | 2100 | 24 |
| Coated mercury-vapor | 3600 | 49 |
| Halophosphate warm-white fluorescent | 2940 | 51 |
| Halophosphate cool-white fluorescent | 4230 | 64 |
| Tri-phosphor warm-white fluorescent | 2940 | 73 |
| Halophosphate cool-daylight fluorescent | 6430 | 76 |
| "White" SON | 2700 | 82 |
| Quartz metal halide | 4200 | 85 |
| Tri-phosphor cool-white fluorescent | 4080 | 89 |
| Ceramic metal halide | 5400 | 96 |
| Incandescent/halogen bulb | 3200 | 100 |
A reference source, such as blackbody radiation, is defined as having a CRI of 100. This is why incandescent lamps have that rating, as they are, in effect, almost blackbody radiators. The best possible faithfulness to a reference is specified by a CRI of one hundred, while the very poorest is specified by a CRI below zero. A high CRI by itself does not imply a good rendition of color, because the reference itself may have an imbalanced SPD if it has an extreme color temperature.
Read more about this topic: Color Rendering Index
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