Search the FAQs

Use the form below to search the FAQs


What is Kelvin Color Temperature?

Technical Answer

The term “color temperature” is widely used – and often misused in illumination work. It relates to the color of a completely radiating (black body) source at a particular temperature and of light sources that color-match such a body. The color temperature of a light source is the absolute temperature of a blackbody radiator having a color equal to that of the light source. Its correlated color temperature is the absolute temperature of a blackbody whose color most nearly resembles that of the light source.


If you would insert an iron rod, (a theoretical black body, or a perfect radiator) into a fire, the iron rod begins to heat up. As the rod heats up, the rod begins to change color. As the rod gets hotter and hotter the rod begins to “glow”. The hotter the rod, the brighter and the lighter the color appears. When this rod reaches the exact color of a common household incandescent light bulb, it is said to give off all its energy at 2700 degrees Kelvin.

If you leave the rod in the fire, and the fire is made hotter, the color of the rod leaves the warm glow of incandescence and brightens to a point higher up the Kelvin level. When the rod reaches a color of a cool white lamp, it is said to give off all its energy at 4,000 degrees Kelvin, etc. If you continue to heat the rod, what happens? The rod will finally reach a “white color” equal to 5,000 degrees Kelvin and higher.

The blue sky you see on a normal clear day is approximately 7500 degrees Kelvin.

Vi-Tek 93® Plus, at 6700 degrees Kelvin, is the brightest fluorescent lamp on the market with a high color rendering of 93. Experts agree that the higher lumen output, higher color rendering and the higher Kelvin temperature allows people to see color almost as it would be outside in the daylight. Better to determine contrast, and affords a much more comfortable work environment

What is the Color Rendering Index (CRI)?

Color Rendering Index (CRI) is a numerical system that rates the "color rendering" ability of fluorescent light in comparison with natural daylight, which has a CRI of 100. This means that a lamp with a CRI of 93 shows colors more naturally than a lamp with a CRI of 62.

Ask a Question

Use the form below to ask a question

Fill in your email address