Color Temperature to RGB

What this tool is used for

• Getting an RGB approximation of a light source's colour temperature.
• Setting a white balance reference for a design or a render.
• Understanding what a bulb's stated Kelvin value looks like.
• Comparing warm and cool light values side by side.
• Producing a tint that matches a lighting condition.

Frequently Asked Questions

What does colour temperature actually measure?

The temperature a black body would have to reach to glow that colour, in kelvin. It is a physics definition, which is why the naming is counter-intuitive: 2700K is 'warm' orange light and 6500K is 'cool' blue-white, the opposite of the everyday sense of warm and cool.

How is the RGB conversion computed?

Through Tanner Helland's piecewise approximation, fitted to black-body data with a break at 6600K: below it red is saturated and green follows a logarithm; above it both red and green follow power laws. It is an approximation, accurate to a few percent across roughly 1000–40000K.

What are the common reference temperatures?

Candlelight around 1900K, incandescent 2700K, warm white LED 3000K, direct sunlight 5500K, overcast daylight 6500K, and clear blue sky as high as 10000K. D65 — 6504K — is the white point sRGB itself is defined against.

Why does the same object photograph differently indoors?

Because the light source's temperature shifts every colour in the scene, and your eye adapts while the sensor does not. That is what white balance corrects: it applies the inverse shift so a white sheet under 2700K bulbs is recorded as white rather than orange.

Is a higher temperature brighter?

No — temperature is hue, brightness is a separate quantity measured in lumens. A 2700K bulb and a 6500K bulb can be identical in output and differ only in colour, which is why lighting specifications quote both and why replacing a bulb by wattage tells you nothing about either.

Common errors and gotchas

• Confusing correlated colour temperature with an actual colour, since many spectra share one value.
• Assuming higher Kelvin means warmer, when it is the reverse of the everyday sense of the word.
• Using the RGB output as a light source's true spectrum, which it is not.
• Applying a screen approximation to a colour-critical print or photography decision.
• Ignoring the display's own white point, which changes how the value appears.