Lumen Output
Lumen is the rate at which a source produces light. The light output is the total amount of light emitted by the source in all directions per unit time. Higher lumens correspond to brighter light while lower lumens correspond to dimmer light. The selected LED lighting should be capable of providing enough light to achieve the proper lighting level required.
Color Quality and Appearance
Objects are not inherently colored, but rather reflect different proportions of radiant energy. Thus, if the light incident on a surface changes, the apparent color of the object may change. Depending on the light source, this shift can be small or large. Color of LED lighting is typically characterized using the correlated color temperature (CCT) and color rendering index (CRI) metrics.
Correlated Color Temperature (CCT)
The correlated color temperature is the absolute temperature (in °K) of a blackbody whose chromaticity most nearly resembles that of the light source. Lamps with a CCT rating below 3200°K are usually considered warm sources, whereas those with a CCT above 4000°K are usually considered cool in appearance. Temperatures in between are considered neutral in appearance. Warm lights are usually used for indoor application whereas cool light is used for outdoors and industrial application. Figure 1 shows the CCT of various light sources.
