The Fidelity Index (Rf) is a measure of the accuracy of color rendering in light sources. It indicates how well a light source reproduces the colors of objects compared to a reference source, such as natural daylight. The Rf value is expressed on a scale of 0 to 100 , with 100 indicating perfect color accuracy.
1. How does the Fidelity Index work?
The Fidelity Index is determined by comparing the colors produced by a light source with a reference source of the same color temperature. This is done through spectral measurements and calculations that analyze the color shift.
📌 Key features of the Fidelity Index (Rf):
- Rf = 100 → Perfect color rendering, identical to the reference source.
- Rf < 90 → Colour deviations visible, suitable for functional applications.
- Rf < 80 → Noticeable colour distortion, less suitable for colour-critical applications.
- Higher Rf means better color accuracy , but does not always mean the most pleasing color reproduction .
2. Difference between Fidelity Index (Rf) and Color Rendering Index (CRI Ra)
| Feature | Fidelity Index (Rf) | Color Rendering Index (CRI Ra) |
|---|---|---|
| Reach | 0 - 100 | 0 - 100 |
| Color models | 99 colors (TM-30-18) | 8 to 15 colours (CIE Ra) |
| Accuracy | Highly accurate, wider spectrum | Less accurate, limited spectrum |
| Used in | Modern LED lighting, high-quality displays | Standard lighting, general applications |
📌 The Fidelity Index (Rf) is more accurate than the traditional CRI (Ra) and is used in advanced lighting systems.
3. Applications of the Fidelity Index
🎭Theatre and studio lighting → Realistic and true-to-life colour reproduction.
🖼 Museums and art galleries → Preservation of original colors during exposure.
📸 Photography and film production → Essential for true-to-life color tones.
🏠 Architecture & Interior Design → Creates natural-looking light.
🖥 Monitors and digital displays → High color fidelity for professional applications.
📌 In professional and artistic environments, a high Rf value (90+) is recommended.
4. Why is the Fidelity Index important?
🔹 Prevents color distortion → Important in detail-oriented applications such as art and fashion.
🔹 Better color consistency → Essential in retail and product presentations.
🔹 More control over lighting → Helps choose the right light source for specific applications.
💡 In short:
The Fidelity Index (Rf) is an advanced method for measuring the color rendering of light sources and is more accurate than the traditional CRI . It is widely used in high-end lighting, photography, museums, and displays for a true-to-life color experience .