Mercury Vapor Lights

Olga in Vancouver asks about Mercury Vapor lights.  Mercury is a "Halide."
 However, MV lamps are typically Mercury Vapor Lamps, which get the light
from an arc in a Mercury Vapor.  They have a VERY narrow spectrum of emitted
light. It is a very poor match for chlorophyll's needs. As a quick
experiment, take a bright colored object under a MV lamp. (A child's toy is a
good example.) It will look WEIRD, because many of the colors will not be
able to reflect the MV light.  High Pressure Sodium would be better - NOT
GOOD - but better, as they have a much wider spectrum. "Mostly" orange, as I

The reason I have some familiarity with those lamps is, I am an amateur
astronomer, and MV light is fairly easy to filter from the telescope, Low
Pressure Sodium VERY easy (Yellow.  Bright yellow. Very narrow spectrum.),
High Pressure Sodium a real nuisance, but basically orange.

 The bottom line is, I do not think you would be pleased with MV lamps.  Bad
color rendition, harsh bluish light.  :-(  

Our "Metal Halide" lamps work on a different principle: The Halide Vapor is a
"preservative" for a tungsten filament, a filament similar to the one in the
common light bulb.  However, because of the Halide Vapor protecting the
filament, the filament can get a LOT hotter without burning out. Thus, the
high CRI from the very HOT Filament. Also greater Lumens per Watt, same

Hope that helps.