High Pressure Sodium and Metal Halide; what is the difference?
Although High Pressure Sodium and Metal Halide are both types of HID (High Intensity Discharge) lights, they emit different color spectrums. Generally High Pressure Sodium (HPS) lamps emit light that is concentrated in the red to yellow side of the spectrum and weak in the blue-violet end. Metal Halide (MH) lamps, by contrast, emit a more balanced light, but are generally concentrated in the blue to yellow side of the spectrum and are weak in the orange to read end. Both types of lighting have their place in an indoor growing environment. Another difference is the lumens per watt of both bulbs. HPS lamps are usually more efficient light producers (more lumens per watt), these lamps produce a range of 100-140 lumens per watt, while MH lamps produce a range of 70-110 lumens per watt. An easy way to tell difference between the two types is by appearance.
