Light Emitting Diodes (LEDs) are light sources that can be substitutes for natural sunlight and some produce full spectrum light to support full cycle cultivation. They can produce light with different wavelengths corresponding to different colors. While choosing LEDs for growing plants, along with lumens or PPF, wattage, and lux, it is important to also consider correlated color temperature (CCT) and color rendering index (CRI) of LEDs because they are important in determining the color characteristics of the light. CRI and CCT give insight into the color quality of the LED. Not all LEDs display the same colored light. While some are warm or soft white, others produce much brighter looking, whiter light. Determining which type of lighting is appropriate will depend on the application. For growing plants, the spectrum of the light source should mimic natural sun light, otherwise your plants will not grow and develop normally.
CCT (Correlated Color Temperature)
Color temperature describes the warmth or coolness of a light source in degrees Kelvin. White light is a combination of different color spectrums. Not all with light is created equal, white LED lights do not emit light energy at all wavelengths equally. At low color temperatures, the light will be more yellow but as the temperature Kelvin increases, the spectrum shifts from red and yellow tinted white, to more bluish white. The ability to perceive colors naturally under different light sources depends on the spectral make-up of a light source. LEDs offer full spectrum including warm white (lower color temperatures), neutral white (3750-5000 K) and cool white (Above 5000 K). LED lights above 5000 Kelvin are often more blueish and closely resemble natural sunlight. For growing plants, full spectrum LEDs with accurate rendering of colors is required because each spectrum initiates different responses from the plants.
CRI (Color Rendering Index)
CRI is a lights’ ability to accurately render all frequencies of color spectrums in comparison with natural sun light. It is helpful in comparing one LED light to another. Items placed under high CRI lights will look the same as they do outside under sun light, whereas the same objects placed under low CRI lights will appear unnatural and dull. CRI is rated on a scale from 1 to 100 with natural sunlight taken as baseline with a value of 100. The higher the CRI value, the greater the color rendering ability and better plant growth. Light sources with good LED quality render CRI close to natural sunlight i.e 100. They offer wide spectral distribution of all wavelengths with high level of color rendering. For instance, conventional bulbs like CFL or halogen emit white light but are not equivalent to LEDs in color quality. For this reason, they are not as effective as LEDs for growing plants. Quality LEDs offer high CRI with different CCT values suitable to the various cultivation needs. Based on the stage of cultivation, LEDs can be tailored to specific color spectral outputs to produce better yields.