Illuminant D65 represents daylight with a color temperature of 6500 Kelvin, while Illuminant D50 represents daylight at 5000 Kelvin; these two Standard Illuminant are used across different industries. Their key difference lies in their Spectral Power Distribution (SPD); D65 contains stronger blue and ultraviolet (UV) components, whereas D50 provides the most neutral color rendering for evaluating printed materials. This makes D50 the essential and universal standard for print quality control, as it minimally influences the sample's color appearance.

D65 is primarily standardized for digital environments and the evaluation of non-print products such as textiles, automotive parts, and displays. In contrast, D50 must be used exclusively in print and prepress inspection stations. Failure to adhere to this vital distinction can lead to Metamerism and a stark color difference between the monitor (often set to D65) and the physical print (which must be viewed under D50). Consequently, for color consistency, both lights must be used in their correct professional environment.