If for some odd reason you’ve been just shopping around for LED lamps (that’s fancy jargon for “light bulbs”) just for the fun of it, you may have seen on the side of the box a number somewhere between 2700K and 6500K and wondered to yourself “What on earth does that mean?”
The Kelvin scale is an absolute thermodynamic temperature scale using as its null point absolute zero where all thermal motion ceases. The scale is named after Lord Kelvin who noticed that when burning a block of carbon it burned a different color the depending on the temperature of the heat source.
In lighting, color temperature is the way we measure color of light output. Most of us are used to a nice warm 2700K that comes from our incandescent lighting in our homes. Offices typically use a “cooler” color temperature in the range of 4100-4500K. The higher on the Kelvin scale you get the bluer the light becomes. I tend to prefer warmer color tones on architectural features and decorative plants and cooler tones in downlighting from trees. Some people don’t like to mix and match but I think in the right application it can look really awesome. See the picture below as an example.
In outdoor lighting, consistent color temperature is much more important than in interior applications. Because of the contrast of light on dark material it’s easy to differentiate a very slight discrepancy in color temperature. As of right now there are not very good standards in marketing of LEDs so 2700K in one manufacturer can look much different in 2700K in another. I will blog more about that in a future blog. In the meantime trust a lighting professional to assist you in selecting the appropriate lamps for you landscape lighting.