What is CRI, and is it good for comparing grow lights?
CRI, or Color Rendering Index, is a quantification of how faithfully a light source reveals the relative color of various objects, as perceived by the human eye, compared to an "ideal" or "natural" light source (a blackbody radiator) of the same color temperature (CCT). Sunlight and incandescent light bulbs have a CRI of 100 - the highest score possible - as they are effectively blackbody radiators, but most other artificial light sources have a lower CRI.
Just because a light source has a high CRI score does not mean it is better for growing plants, however. A light source can have an excellent CRI but lack wavelengths of light that plants most-efficiently use for photosynthesis. High Pressure Sodium (HPS) lights, long used as grow lights, have a very low CRI of 24- so just because the CRI score is low does not mean that the light isn't a good grow light either. This makes CRI fairly meaningless for evaluating how well a light will grow plants.
There are two factors that affect the CRI score: how continuous the spectrum of light is, and how closely the spectral power distribution (SPD, which is the relative intensities of different wavelengths of light) match a perfect "blackbody radiation" curve of the same correlated color temperature (CCT).
For light sources that have discontinuous SPD, such as fluorescent and HPS lights, this negatively affects their CRI because objects that reflect wavelengths not present in the light source do not appear to be the same color as they would under a continuous-spectrum light.Various lights' spectrums and CRI's
|Select Spectral Data|
Because Black Dog LED lights do not have a CCT (color temperature), it is technically impossible to calculate a CRI for our lights, as they cannot be compared to an "ideal" light source with the same CCT. Just because our lights do not have a CRI (or CCT) does not mean that it is difficult to see colors or discern between colors under our light; since our lights' spectrum is continuous, it is easy to see subtle variations in color when working under our lights. However, as our spectrum has more blue and red compared to other colors, the blue-ness or red-ness of objects viewed under our lights may be slightly exaggerated.
Our Grow Glasses correct for our Phyto-Genesis Spectrum's® SPD and allow you to view your plants with perfect color rendition; in effect the glasses give our lights a perfect 100 CRI.