I have to agree the Phosphur Coated Mercury Lamps give more Light than the Clear Lamps example a 100w Clear Mercury Lamp produces 4000 Lumens whilst the Phosphor Coated Lamp produces 4500 Lumens,also the Phosphor increases the CRI too whilst the Clear Mercury Lamp gives a cold Harsh Light at 5700 deg K and CRI of 16 to 25 the Phosphur Coated Lamp warms the light to 4000 deg K and increases the CRI to 40.
All the Best for 2011
Colin