Outdoor Lighting Glossary
Come across a lighting word you aren't sure of? Completely new to the world of lighting? We feel your pain! Here you will find a collection of terms and concepts that should help to make your life easier.
Have you come across a term that we don't have? e-mail the Webmaster and we'll add it!
Select the first letter of the word from the list above to jump to appropriate section of the glossary.
Maintained Footcandles - Footcandles calculated through application of light loss factors.
Maintenance Factor (MF) - A factor used in calculating illuminance after a given period of time and under given conditions. It takes into account temperature and voltage variations, dirt accumulation on luminaire and room surfaces, lamp depreciation, maintenance procedures and atmosphere conditions.
Matte Surface - A non-glossy dull surface, as opposed to a shiny (specular) surface. Light reflected from a matte surface is diffuse.
Mean Lumens - Amount of light output at 40% of lamp life
Mercury Lamp - A high intensity discharge (HID) lamp in which the major portion of the light is produced by radiation from mercury. Includes clear, phosphor-coated and self-ballasted lamps.
Mercury Vapor Lamp - A type of HID lamp in which the major portion of the light is produced by radiation from mercury vapor. Emits a blue-green cast of light. Available in clear and phosphorcoated lamps.
Mercury vapor lamps operate very similarly to traditional metal halide lamps in that they incorporate the same type of starting probe (electrode). Their efficiency and lumen maintenance is slightly less than metal halide units and substantially less than high pressure sodium. However, mercury vapor lamp life is close to that of high pressure sodium. While "color corrected" versions are available, the average color rendering index (CRI) is poor and similar to that of high pressure sodium, 15-20.
Mesopic vision - Vision intermediate between photopic and scotopic vision.
Metal Halide Lamp - A high intensity discharge (HS) lamp in which the major portion of the light is produced by radiation from mercury. Includes clear. phosphor-coated and self-ballasted lamps.
Traditional metal halide lamps incorporate a starting probe (electrode) to initiate an arc via high open circuit voltage. The iginition time is negatively affected by this low voltage starting technique, with the run up time of around four minutes and a restrike time running anywhere from 15 to 20 minutes. The efficiency (lumens/watt) of traditional metal halide lighting systems is between 50% and 60% that of a comparable high pressure sodium system. However, the white light produced by these lamps renders a color quality (CRI) of 65-70, three times better than high pressure sodium.
MOL - The Maximum Overall Length of a lamp from the tip of the base to the top of the glass.
MR16 - A low-voltage quartz reflector lamp, only 2 inches in diameter. Typically the lamp and reflector are one unit, which directs a sharp, precise beam of light
