How To Calculate Color Temperature

Color Temperature Formula:

\[ CT = 449 n^3 + 3525 n^2 + 6823.3 n + 5520.33 \] \[ n = \frac{x - 0.332}{y - 0.1858} \]

Color Temperature (CT):

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1. What Is Color Temperature?

Color temperature is a characteristic of visible light that describes its color properties. Measured in Kelvin (K), it helps define the appearance of light sources from warm (yellowish) to cool (bluish) tones.

2. How Does The Calculator Work?

The calculator uses the color temperature formula:

\[ CT = 449 n^3 + 3525 n^2 + 6823.3 n + 5520.33 \] \[ n = \frac{x - 0.332}{y - 0.1858} \]

Where:

\( CT \) — Color Temperature in Kelvin (K)
\( n \) — Intermediate calculation value
\( x \) — x coordinate in CIE 1931 color space
\( y \) — y coordinate in CIE 1931 color space

Explanation: The equation converts chromaticity coordinates (x, y) from the CIE 1931 color space to an approximate correlated color temperature value.

3. Importance Of Color Temperature Calculation

Details: Accurate color temperature calculation is essential for lighting design, photography, cinematography, display calibration, and ensuring consistent color reproduction across different media.

4. Using The Calculator

Tips: Enter the x and y chromaticity coordinates from CIE 1931 color space. Ensure y ≠ 0.1858 to avoid division by zero. Values should be within valid CIE 1931 chromaticity range.

5. Frequently Asked Questions (FAQ)

Q1: What is the CIE 1931 color space?
A: The CIE 1931 color space is one of the first mathematically defined color spaces, created by the International Commission on Illumination (CIE) in 1931, that maps human color perception.

Q2: What are typical color temperature values?
A: Common values include: candlelight (1500-2000K), incandescent bulbs (2700-3000K), daylight (5000-6500K), and overcast sky (6500-10000K).

Q3: How accurate is this calculation method?
A: This cubic approximation provides good results for most practical applications, though for precise scientific work, more complex methods or lookup tables may be used.

Q4: Can this formula be used for all light sources?
A: The formula works best for Planckian radiators (black body radiation) and light sources that closely approximate black body radiation.

Q5: What if I get negative or extremely high values?
A: This may indicate invalid input coordinates outside the expected range for typical light sources. Verify your x and y values are correct.