halides of one or more of the rare earth elements of the series dysprosium dy holmium ho thulium tm cerium ce praseodymium pr scandium sc neodymium nd europium eu lutetium lu and lanthanum la can be alternatively or jointly used such that the total molar quantity of halides of na and mg and of the rare earth elements present in arc discharge chamber 20 is between 95 and 99 3 in one example a halide of dysprosium can be used in discharge chamber 20 having a molar quantity that is between 0 to 20 of that total molar quantity of all halides present therein in the following table 1 for a pair of lamps of one correlated color temperature and table 2 for a pair of lamps of another correlated color temperature characteristics are presented in tabular form of fig1 and 2 ceramic arc discharge chamber metal halide lamps as just described with a small amount of tli in the chamber materials compositions and of corresponding typical commercially available lamps with typically used doses of tli in the chamber materials compositions thereof the data are listed for these lamps operated both at the rated lamp power of 150 w and at 50 of rated lamp power in a dimmed condition lamp characteristics of a 3500k correlated color temperature lamp with a very low tli dose and a 3500k correlated color temperature lamp with a typical tli dose lamp characteristics of a 3000 k correlated color temperature lamp with a very low tli dose and a 3000 k correlated color temperature lamp with a typical tli dose duv is a parameter to represent a comparison of light.