Multifaceted reflector
MR16 (sometimes referred to as MR-16) is a standard format for halogen reflector lamps made by a variety of manufacturers. MR16-compatible LED lamps are also available. MR16 lamps are regularly used in place of compact fluorescent lamps or standard incandescent light bulbs for applications including residential lighting and retail lighting. MR16 lamps were originally designed for use in slide projectors. They are well suited to a variety of applications that require directional lighting of low to medium intensity, such as track lighting, recessed ceiling lights, desk lamps, pendant fixtures, landscape lighting, retail display lighting and bicycle headlights.
Designation
MR16 is a coded designation in which MR stands for Multifaceted Reflector and 16 is the number of eighths of an inch the front is in diameter, in the case of MR16: 2 inches.
Halogen MR16 Characteristics
Halogen MR16 lamps consist of a halogen capsule (bulb) integrated with a pressed glass reflector. The reflector of an MR16 lamp is 2 inches (50mm) in diameter. The base conforms to Bipin GU5.3 standard. The compact size of the MR16 allows for much smaller, more discreet fixtures than the incandescent reflector bulbs that pre-dated MR16s.
The reflector controls the direction and spread of light cast from the lamp. MR16 lamps are available with different beam angles from narrow spot lights of as small as 7 degrees to wide flood lamps of 60 degrees.
"MR" refers to multifaceted reflector, indicating that this reflector is usually shaped with multiple small facets. This multifaceted reflector gives a soft edge to the area illuminated by the lamp. MR16 lamps are also available with smooth reflectors, resulting in a sharper fall-off to the illuminated area. "16" refers to the maximum diameter of the lamp in eighths of an inch, 16/8" or 2 inches (5cm).
In less-expensive lamps, the reflector has an aluminium coating that reflects all light. In more-expensive lamps, the reflector commonly has a dichroic coating that reflects particular frequencies of the visible spectrum in the direction the lamp is facing, while not reflecting infrared light. By not reflecting infrared light (which produces heat), these lamps reduce the amount of heating of the subject they are focussed on. The combination of the halogen light source and dichroic coating also means that these lamps provide a high color rendering index and a higher color temperature than standard incandescent bulbs. This makes them well suited to applications where color rendering is important, such as retail display lighting.
The brightness of MR16 lamps can be adjusted when used with appropriate fixtures and dimmers. However, the color temperature changes significantly when the lamp is dimmed.
MR16 lamps produce significant heat, and care must be taken to avoid contact with skin or proximity to flammable materials when the lamp is on or has been on recently.
Halogen MR16 lamps are typically more efficient than standard incandescent bulbs, but not as efficient as fluorescent lamps or LED technology. MR16 lamps typically have a life expectancy of 1000 to 3,000 hours.
With both types of incandescent bulbs, useful life can be considerably shortened if their filaments experience mechanical shock or vibration. Using an electronic transformer with a 'soft start' feature can considerably extend life as it reduces the characteristically high inrush current which occurs shortly after switch on. Additionally, it can be less strainful on the eyes, giving the pupils more time to react to a sudden increase in environmental lighting level.
MR16 lamps, like all quartz-halogen lamps, produce substantial amounts of ultraviolet light. Usually, this must be filtered out. Also, the quartz capsule of the lamp sometimes ruptures ("explodes") upon failure of the lamp. For these two reasons, some MR16 lamps include a cover glass that serves as an integrated ultraviolet filter and explosion shield. MR16 lamps lacking this cover require the use of a fixture that incorporates an external piece of glass specifically designed to provide this protection.
MR16-Compatible LED Lamps
MR16-compatible LED lamps are also available. They are similar in shape to halogen MR16 lamps, and can be used in most fixtures designed for MR16 lamps. The same is true of MR11-compatible LED lamps.
Versions of the led lamps have been patented in the UK[citation needed]. Due to the low heat and power consumption they have been produced from plastic although this does not affect their efficiency. Their non-polarised AC/DC operation with current limitation over a wide voltage range 11.5 ~ 18 volts as a standard 12 volt version, allows a wide range of usage.
Quoted average rated life given by manufacturers is typically 30,000 - 50,000 hours depending on the product in question. This amounts on average to 1250 - 2080 days of continuous operation, or roughly three to six years.
Fixtures designed for halogen MR16 or MR11 lamps that use electronic power supplies may need to be retrofitted with "LED-compatible" power supplies. This is because these electronic power supplies require a minimum power lamp in order to function, and the LED lamps may be below this power. Fixtures that use magnetic transformers can generally be used with LED lamps without modification.
Products from some manufacturers incorporate full wave rectification so that either AC or DC can be used, whilst others require a DC supply and correct polarity must be observed.
At this time, there are few standards for MR16 and MR11 compatible LED lamps. As such there are a wide variety of designs of such LED lamps, varying significantly in beam control, light quality, efficiency and luminous power.
Unlike halogen MR16s, such lamps often do not have the multifaceted reflectors that give MR16s their precise beam control in a variety of beam spreads. Some rely on the optics of the LED(s) to control the beam. They may also have a simple cut-off apertures that limit beam spread. Others have individual reflectors for each LED.
As with other LED lamps available today, the quality and color temperature of the white light produced by such lamps varies. Many tend towards the blue end of the spectrum, being even "cooler" than fluorescent. Because of these variations, some MR16 and MR11 compatible LED lamps create significantly more natural looking light than others.
The least efficient of these lamps produce about 26 lm/W (lumens per watt), which is similar to the efficiency of halogen MR16s. The most efficient of these lamps available today produce about 70 lm/W, which exceeds the efficiency of compact fluorescent lamps.
In terms of total luminous power, such lamps range from being significantly less powerful than their halogen counterparts, to being comparable to the lower power halogen MR16s. The brightest available halogen MR16s are still significantly brighter than the brightest available LED versions.
Variations
MR16 lamps most often operate at 12 volts, although they are also available in other voltages. The common 12 volt MR16 lamps therefore require a magnetic or electronic transformer (sometimes misnamed as a ballast) to convert the 120 or 240 volt mains voltage to the operating voltage required by the lamp. Note that although halogen MR16 lamps can usually operate on either AC or DC voltage, some LED devices require DC voltage and as such will require a rectifier in the unit if AC is to be used.
Certain MR16 lamps can operate directly on the mains voltage. These lamps typically use a GU10 turn and lock base so they can't be accidentally interchanged with low voltage lamps. As such, they are often referred to as GU10 rather than MR16 lamps. Because of their use of much-finer wire, the filaments of lamps that operate directly from mains voltage are much more fragile than those used in low-voltage lamps.
Low-voltage MR16 lamps almost always have ANSI standard GU5.3 two-pin bases. MR16 lamps with an integrated transformer are also available. These lamps have screw bases to fit standard medium-base Edison sockets.
Smaller lamps are also manufactured in the less common MR11 and even less common MR8 formats, which have reflectors that are 1 3/8 inch (11/8" or 35 mm) and 1 inch (8/8" or 25 mm) in diameter, respectively. These smaller lamps appear very similar to MR16 lamps, also featuring similar multifaceted reflectors that are available in a variety of beam spreads. Their smaller size makes possible even smaller fixtures, but limits them to lower powers. MR11 and MR8 lamps have pins placed more closely together, preventing them from accidentally being interchanged with MR16 lamps.
ANSI Designations
The following ANSI standard codes are used to designate certain power and beam angle combinations for MR16 lamps. Many manufacturers use these standard codes for lamps matching these specifications:
- ESX: 20 watt, 10 degree beam (20MR16/10°)
- BAB: 20 watt, 40 degree beam (20MR16/40°)
- EXT: 50 watt, 15 degree beam (50MR16/15°)
- EXZ: 50 watt, 25 degree beam (50MR16/25°)
- EXN: 50 watt, 40 degree beam (50MR16/40°)
- FPA: 65 watt, 15 degree beam (65MR16/15°)
- FPC: 65 watt, 25 degree beam (65MR16/25°)
- FPB: 65 watt, 40 degree beam (65MR16/40°)
- EYF: 75 watt, 15 degree beam (75MR16/15°)
- EYJ: 75 watt, 25 degree beam (75MR16/25°)
- EYC: 75 watt, 40 degree beam (75MR16/40°)
Note that MR16 lamps are available in many other power and beam combinations than those available above. For this reason, MR16 lamps are also often labeled according to beam spread abbreviations. Note that these while these abbreviations are commonly used, the angles associated with these abbreviations vary slightly from manufacturer to manufacturer. These are typical beam angles for these beam spread abbreviations
- VNSP (Very narrow spot): less than 8 degrees
- NSP (Narrow spot): 8-15 degrees
- SP (Spot): 8-20 degrees
- NFL (Narrow flood): 24-30 degrees
- FL (Flood): 35-40 degrees
- WFL (Wide flood): 55-60 degrees
- VWFL (Very wide flood): 60 degrees or more