Optimized phosphor system for improved efficacy lighting sources

An arc discharge lamp having an improved luminosity for a given color rendering index and color coordinated temperature, the lamp comprising

• a lamp envelope enclosing a discharge space and having an inner surface;
• an ionizable medium within said lamp envelope comprising mercury and an inert gas;
• first and second electrodes;
• and
• a phosphor layer comprising a phosphor blend on said inner surface, said blend comprising:
• a blue phosphor having an emission peak at 440–490 nm, a blue-green phosphor having an emission peak at 475–525 nm, a green phosphor having an emission peak at 515–550 nm, an orange phosphor having an emission peak from 550–600 nm, a deep red phosphor having an emission peak at 615–665 nm, and a red phosphor having an emission peak at 600–670 nm.