The Color Rendering Index is a measure of how faithfully light from a source will reproduce colors. Incandescent bulbs have a CRI of 100 – which is taken as a perfect score.
Incandescent light is the light source with the best CRI. It serves an index of 100 because the spectrum provides all wavelengths. An incandescent light bulb can be compared to the sun, the sun is our natural light source having an CRI of 100 too. CFLs normally provide a CRI80.
That is the single most important reason that CFLs have not been able to replace the incandescent bulb despite heavy promotion. There are CFLs that produce warm light. But to produce a warm light the glass coating of a CFL has to be suitable doped with additives that essentially absorb light in one part of the spectrum and emit light in another part. This further reduces the lighting efficiency of CFLs.
LED products and systems are in a different league altogether. If you look at images produced by a LED projector, the vibrant colors reproduced and its superiority over two centuries old incandescent technology becomes apparent. LED light sources are among other light sources superior in lighting effciency and quality.
If you look at the history of lighting, the first electrical and popular wide-spread lamp has been the incandescent one. Other light sources that followed took advantage of newer technology background as well as other possibilities of producing light. Each light source is different, with advantages as well as disadvantages and it is just natural that older light sources will phase out because others are better than the old technology. LEDs are anyway the best lighting source you can get right now for many applications.
Visual tests have shown that the definition of the CRI needs to be reviewed. Scientists asked observers to rate color schemes, which are used to define the CRI of a lamp, under different light sources. The comparisons of LED with lamps of a higher CRI have been surprising.
The observers had the visual impression that both light sources would be equal in lighting quality, although the LED had per definition a worse CRI. One needs to know that the definition of the CRI has been taken part within the time of the invention of discharge lamps. Regarding the basis of the color rendering index, the testing method is taking into consideration 14 different standardized colors.
But only the first eight colors of the reference color scheme are taken into the calculation of the CRI, surprisingly that are pale pastel colors. Now that standard itself is under scrutiny. There is a debate to change the standards to reflect the reality of today’s lighting technology.
