What is CRI(Color Rendering Index)?

- Dec 20, 2018-

The ability of artificial white light to restore the natural color of an object is measured by the Color Rendering Index (CRI). This method uses a comparison of medium brightness values and chroma to determine CRI.

    The average value of R1 to R8 is the average color rendering index (Ra). The CRI test is often R9 or even too low, sometimes negative values appear. This indicates that the white light produced by the LED lacks red light radiation, and the low R9 value will affect R1-R8. As a result, the average value of Ra is lowered. For the warm color temperature range, Ra measures the color rendering of the LED light source. For an LED light source with a high color temperature range, Ra measures the color rendering property with a certain distortion.

    Since the national standard stipulates that Ra can be used to judge the color rendering, we can only use this parameter as a reference. The white light with a color temperature above 4000K should not rely too much on Ra to evaluate the color rendering. The visual contrast of the same color temperature should be used, so that the contrast can be actually manipulated. The effect is better than the dependency test Ra. Of course, for professionals, the value from R1-R15 can be concluded.

    The color temperature and color rendering of white light are the main indicators to measure the quality of lighting. The consistency of the color temperature of the lamp in the same batch will be different. It needs to be separated after color separation. The color temperature mainly investigates the consistency and color temperature drift. Chromaticity, which requires at least 65 or more to be used in lighting, affects the color temperature and color rendering of the lamp bead:

    1) Phosphor quality and ratio, the better the quality of the phosphor, the better the color temperature consistency, the smaller the color temperature drift, the more scientific the phosphor ratio, the better the color rendering.

    2) The larger the drive current, the color temperature will drift to a higher color temperature.

    3) The worse the quality of the phosphor, the easier the color temperature drifts, and the light decay is easy to occur.

    4) The operating temperature also affects the color temperature drift.

    5) The worse the chip quality, the worse the color temperature consistency.

    6) The same material and packaging process products, high color temperature (such as 6500K) consistency is easier to do, low color temperature (such as 3000K) requires a smaller color temperature segment.

    LED lighting products are greatly affected by the choice of LED lamp beads. When manufacturing and selling LED lighting products, more attention should be paid to the quality identification of LED lamp beads. LED lighting products are generally composed of multiple LED lamp beads. Blurring the bad quality of the lamp bead, the product manufacturer needs to start from the parameter analysis of the lamp bead to identify the quality connotation of the product and minimize the operational risk.