One aspect of lamp colour is its colour appearance; whether the light from the lamps looks ‘warm’ or ‘cool’, measured by the correlated colour temperature (CCT). Lamps with a warm appearance having a CCT of 2700 – 3000K are generally considered appropriate in a domestic setting. Lamps of 4000K and above are considered ‘cool’ and are more appropriate for office and some retail applications.
Ceramic metal halide (CMH) lamps combine high output with great colour rendering and good efficiency. They produce light by passing an electric arc through a mixture of gases. In a metal halide lamp, the compact arc tube contains a high-pressure mixture of argon, mercury, and a variety of metal halides.
The binning of LEDs is a practice used by LED manufacturers to manage the variation of LED performance that is inherent in the mass production. LEDs of similar appearance to the human eye are put in different boxes, or bins. LEDs from the ‘best’ bins are more expensive. Additionally LED manufacturers often operate slightly different binning policies from each other.