CRI stands for color rendering index. But before we can really understand what CRI is we first have to understand what COLOR is. The photographer Paul Outerbridge observed “No object of itself alone has color. We know that even the most brightly colored object, if taken into total darkness, loses its color. Therefore, if an object is dependent upon light for color, color must be a property of light.”
Color rendering index (CRI) is the measure of how well a light source accurately reflects all frequencies of its color spectrum. It’s based on a scale of 1-100. The lower the rating the less accurate the color of the object being lit is reproduced. If you ever walk in a parking lot lit with High Pressure Sodium lamps (which have a CRI of about 24) you may have a hard time telling a red car from a blue car. Or have you ever gone shopping and bought a red shirt and got home and realized it was orange? That’s because the CRI of the fluorescent shop lights (if they are cheap) is lower than the CRI of your incandescent lighting at home.
In most outdoor lighting projects LEDs are the lighting source of choice because of their excellent energy efficiency and long lamp life. But you get what you pay for. More expensive LEDs will have a much better CRI (up to 98) than the ones you will find at big box stores. And again, because of the contrast of light on dark surfaces in landscape lighting CRI is VERY important. Be sure you ask a lighting professional before making any purchases.