The Color Rendering Index (CRI) of a bulb specifies on a scale of 1 to 100 how colored objects appear under that bulb’s light compared to their appearance in daylight. A CRI of 100 means no difference, while a low CRI could mean a big difference. Incandescent lamps typically have CRIs above 90, but that doesn’t mean that they always give suitable results. Suppose, for example, we wish to illuminate white cabinets in a kitchen or a hospital examination room. A design objective might be to enhance the impression of whiteness, cleanliness and sterility. In this case, the color temperature of incandescents would be too low to achieve the desired effect. As a general rule, one should, therefore, select color temperature first, then select the lamp giving the optimum CRI for the application.

Most fluorescent lamps operate at 3000K to 4100K,with a CRI from the low 50s to 86, but recent technology gains now give us fluorescents with CRIs above 90.

Ballast Technology

All fluorescent lamps require ballasts, which stabilize and control the electrical current that gets sent to the lamp. These ballasts are available in two primary types: magnetic and electronic. While magnetic ballasts use long-standing technology and last for 20 years or more, electronic ballasts have the edge in performance and, because they reduce perceptible flicker, health considerations. Virtually all compact fluorescent lamps specified today use electronic ballasts.