I was just wondering why mercury vapor lamps get dimmer and dimmer as they age. They don't seem to "burn out" the way other HID lamps do, they just keep getting dimmer until they are practically a night light bulb.
Is this why MV has gone by the wayside? They do still seem popular in a lot of places, like those barn lights and for parking lot lights. The bulbs only cost about $10.
Metal halide, which is basically just an improved mercury vapor lamp, has the same lumen drop off characteristic as MV, though not as bad.
Peter
