E27 Dusk to Dawn LED Daylight Sensor Bulb with Dual Photo Sensor Auto On/Off Night Light Security Light

The color temperature of a light source is taken from the temperature of a perfect black body radiator that radiates light with an appearance similar to that of the light source. It is measured in absolute temperature; Kelvin (K). Interestingly,
Although red is associated with hot colors and blue with cool colors, blue appears higher on the blackbody curve
The temperature is higher than red. A more intuitive example of this apparent color temperature contradiction can be seen in candlelight, which has a warm reddish-orange glow but actually has a low Kelvin temperature of 1850K. Therefore, those with a higher color temperature (above 5000K) are called cool colors (blue-white); lower color temperatures (2700 – 3000K) are called warm colors (yellow-white to red).

The Color Rendering Index (CRI or Ra) is a quantitative measurement used to evaluate the ability of a light source to faithfully reproduce the color of an object. To objectively compare the color rendering characteristics of any light source, the CIE's standardized measurement uses a scale from 0 to 100 (poor to excellent). When an object is exposed to a specific light source, the color change of 14 standard colors is calculated and then compared with a reference light source of the same color temperature (blackbody* is used for daylight with a color temperature up to 5000K and above). The CRI of a pair of light sources can only be compared if they have the same color temperature. Choose the CRI scale so that the CRI rating for an ideal blackbody light source, such as an incandescent or halogen lamp, is defined as 100. For light sources that emit a discrete spectrum (such as LEDs and discharge lamps), the CRI can be any value between 0 - 100. As a rule of thumb, the more the spectrum is filled across all wavelengths (380–760nm), the better the color rendering of the light source The better, but a high CRI measurement essentially means lower efficiency (since the less efficient wavelengths are also represented in the spectrum). * A black body is a theoretical object that absorbs all incident electromagnetic radiation and, due to its ability to absorb all wavelengths, is the best emitter of thermal radiation. It radiates a continuous spectrum that depends on body temperature.