PAR stands for Parabolic Aluminized Reflector. A parabolic reflector has a single focal point at which the light source is placed. The properties of a parabolic reflector are that all the light from the source that hits the reflector is reflected in parallel rays. This is the same principle behind satellite and microwave dishes. The parabolic reflector can be used to produce very narrow concentrated light beams as in an ACL, or through the use of diffusing lenses like in PAR lamps can produce wider beams.
The most common PAR lamps are sealed beam lamps where the filament, reflector, and lens are all part of the same unit. A variant of the PAR lamp family is the MR lamp, which, while using a parabolic reflector, lacks a lens to spread the light, instead relying completely upon the reflector to do the focusing. As with all lamps, PARs are measured in eighths of an inch, such that a PAR 64 is 8 inches in diameter and an PAR-16 is 2 inches in diameter. Common PAR sizes are 16, 20, 36, 38, 46, 56 and 64, with common MR lamp sizes being 11 and 16.
PAR Lamps do have different beam angles. For the PAR64, these are denoted as follows:
The MR-16 can follow the same guidelines as above, but often are just denoted by field angle, and they are also available in both 120v and low voltage variations.
- WFL - Wide Flood - (ANSI code: FFS, for 1000W)(UK-nomenclature: CP95), Field Angle: 45°x71°, Beam Angle: 24°x48°; BCP: 40,000
- MFL - Medium Flood - (ANSI code: FFR, for 1000W)(UK: CP62), Field Angle: 21°x44°, Beam Angle: 12°x28°; BCP: 125,000
- NSP - Narrow Spot - (ANSI code: FFP, for 1000W)(UK: CP61), Field Angle: 14°x26°, Beam Angle: 7°x14°; BCP: 330,000
- VNSP - Very Narrow Spot - (ANSI code: FFN, for 1000W)(UK: CP60), Field Angle: 10°x24°, Beam Angle: 6°x12°; BCP: 400,000
- ACL - Aircraft Landing Lights (Most common is PAR64-ACL 28V-250W [GE4552], OR 28V-600W [GE4559]; but ACLs also can be found in PAR36, 38, 46 and 56 sizes, and in various voltages and wattages. The PAR36 varieties are often called "pin spots" or "rain lights")
Most often in theatre PAR lamps are used in conjunction with PAR Cans. A PAR Can is literally just a housing to hold the PAR lamp, attach it to a lighting position, and hold accessories like color or barn doors. According to James Moody's book Concert Lighting, in the early days of Rock & Roll lighting, technicians adapted the film/studio ColorTran CineQueen PAR fixture; and then in 1966 Bill McManus convinced Altman Lighting to manufacture a fixture that moved the color media away from the lamp to extend the color's life. Recently discovered evidence shows that Ariel Davis Manufacturing Company sold a PAR Can as early as 1960--see the thread http://www.controlbooth.com/forums/lighting-electrics/18874-par-acl-par-can-invention.html. Ariel Davis also used the PAR64-NSP as the source in a framing spotlight, the ARIELITE® PAR FRAMER; see http://www.controlbooth.com/forums/lighting-electrics/5916-electro-controls-3201-3214-ers.html. In the UK, James Thomas Engineering made lighter and less-expensive cans from spun aluminum, and affixed them six to a IWB on 15" centers, creating the PAR-Bar. From http://www.pixelpar.com/pixelrange/company.htm :
The ETC Source Four PAR, and Altman StarPar (and other copies), technically aren't PAR-cans, as they don't use a PAR lamp, but since they exhibit most of the same characteristics, they are included in the PAR Can category. Instead, they use an individual lens, reflector and lamp, that allows for more economical lamping and storage practices.
Until at least 1985, many theatrical lighting designers shunned the PAR can for use in the theatre, considering it an uncontrollable fixture only useful for "rock show" lighting. Today, the PAR has replaced the Fresnel as the second most popular theatrical fixture, behind the ERS. In 1999, ETC introduced the PARnel, intended to combine the best attributes of the PAR and the Fresnel.
PDF of datasheet for General Electric PAR64 lamps: View attachment 4192