CRI AND WHY IS IT IMPORTANT
One must pay more attention to the importance of Colour Rendering Index (CRI) in lighting, especially in LED lighting and LED Tubes. It affects the perception of Colours in various settings. Here's why it is important:
Overview of CRI
- CRI Definition: A metric that measures the accuracy of a light source in rendering Colours compared to natural light.
- Scale: Ranges from 0 to 100, with higher values indicating better Colour accuracy.
CRI Levels
- 80 CRI:
- Considered the baseline for acceptable Colour quality.
- Common in standard LED and fluorescent lamps.
- Suitable for low-traffic areas (e.g., hallways, garages) but not recommended for kitchens or bathrooms due to poor Colour differentiation.
- 90 CRI:
- Viewed as a premium option.
- Provides noticeable improvements in Colour clarity.
- Ideal for living spaces like bedrooms and dining areas, where accurate Colour perception is beneficial.
- 95 CRI：
- Offers excellent Colour accuracy, crucial for professionals like artists and interior designers.
- Helps in achieving a cohesive aesthetic in interior spaces, although the average person may not discern much difference from 90 CRI.
R9 Value
- R9 Metric: Measures the rendering of red Colours specifically.
- R9 values correlate with CRI levels (approximately 25 for 80 CRI, 50 for 90 CRI, and 90 for 95 CRI), highlighting the importance of red in Colour perception, especially for skin tones.
CRI CALCULATION
- CRI is computed by comparing the appearance of eight standardized Colour swatches under a light source to their appearance under natural light. The average difference from this ideal is used to derive the CRI score.
Government Green Procurement
- Hong Kong Government Environmental Department specifies that all lighting procured for government departments shall have a CRI of 80 or above.
CONCLUSION
The choice of CRI should depend on the specific application and sensitivity to Colour quality. Higher CRI lighting typically comes at a higher cost and lower efficiency, making it important to balance these factors against the needs of the space and its occupants.
When procuring LED and traditional lamps e.g. LED tubes with low CRI i.e. 80 (e.g. 730, 740, 765 colour temps) or below one should note that these lamps are lower quality and are much more cheaper to manufacture and it does not meet baseline colour quality and are generally not recommended to be used in government departments.