Types of light bulbs or lamps (C) Daniel Friedman Definitions of Common Lamp (Light Bulb) Abbreviations & Types, Explanation of Color Temperature & CRI Scale for light bulbs

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Light bulb type codes, abbreviations, features: here we define the different types of lamps or bulbs used in lighting fixtures. We provide a table of Definitions of Common Lamp (Light Bulb) Abbreviations & bulb Types and we explain the CRI scale for lighting and we discuss the color temperature of different types of light bulbs or lamps. We define light bulb (lamp) brightness, define lumens, & discuss light bulb light output in lumens.

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Definitions of Common Lamp (Light Bulb) Abbreviations & Types

Halogen interior flood lamps (C) Daniel FriedmanThis article series details guidelines for selecting and installing interior lighting to meet the requirements for different building areas. This article includes excerpts or adaptations from Best Practices Guide to Residential Construction, by Steven Bliss, courtesy of Wiley & Sons.

[Click to enlarge any image]

Also see LIGHTING, INTERIOR GUIDE our home page for information about all lighting topics relating to building interior

At left are two indoor halogen flood bulbs, from left a GU/10 and at right an MR-16. These abbreviations and their meanings are explained below.

There are literally thousands of lamps to choose from, but the most common in residential lighting are standard incandescent A lamps, 120-volt BR and PAR directional lamps, and low-voltage PAR and MR lamps, along with a variety of tubular and compact fluorescent's.

How to Read Bulb & Lamp Abbreviations and Codes

While different lamp manufacturers use different codes and abbreviations to label their lamps, most list the wattage first, followed by the bulb shape, width of the bulb (in eighths of an inch), and additional information about the shape and beam angle.

For example, a 50PAR36/H/NSP8° is a 50-watt PAR lamp, 36/8 (4-1/2 ) inches across, halogen with an 8-degree narrow spot beam.

Common abbreviations for types of lamps (light bulbs)

3 Bulb Types (C) D FriedmanCandle, Globe & General Usage Bulbs

The three lamp or light bulb shapes shown at left are referred to (left to right) as candle light (lampe flamme), globe light (lampe globe), and general purpose light (lampe d'usage general).

All three of these lamps operate at 120V.

The center globe is actually an LED adapted to globe format and with a removable base to permit its use in the same sized smaller base as the candle lamp at left.

Light Bulb Abbreviations

In a next level fo detail in lamp specification the codes below are defined as shown.

  • A: General incandescent. (photo at left, bulb at far right)
  • BR: Incandescent, bulged reflector lamps, which replaced the older “R” lamps. These produce up to twice the light in footcandles on the subject as A lamps.
  • F: Fluorescent (photos below, leftmost image)
  • CF: Compact fluorescent (below, second from left. Shown is a GE Helical 20W 120VAC 50Hz 300mA bulb bearing a UL Listing #6649 intended for use in dry locations and not in fully-enclosed recessed light fixtures.)
  • G: Globe, incandescent.
  • GU: (GU/10), general use halogen indoor flood (third photo below from left, leftmost bulb of the pair, 12-Volts)
Fluorescent lamp (C) Daniel Friedman Fluorescent lamp (C) Daniel Friedman Fluorescent lamp (C) Daniel Friedman Fluorescent lamp (C) Daniel Friedman
  • H: Halogen.
  • IF: Inside frost.
  • MR-16: Multifaceted reflectors – low-voltage(12-V) halogen lamp with faceted mirrors that provide superior beam control. Available in numerous beam widths. (third photo above from left, rightmost bulb of he pair) The bulb shown is an "indoor flood" and has a 40 degree angle beam.
  • NSP: Narrow spot.
  • PAR20, 30, 38: Parabolic aluminized reflector—A halogen lamp protected by a heavy glass lens. PAR lamps provide excellent beam control and produce up to four times the light on the subject as A lamps.
  • PAR36: Low-voltage halogen lamp with superior beam control over longer distances.
  • R: Reflector.
  • RSC: a bulb base design used in halogen work lights such as the rightmost bulb shown in the photos above. The bulb shown is a 100-Watt 120-Volt lamp used in work lights and in outdoor security lights.
  • SB: Silver bowl, which indicates that the bottom of the lamp is opaque and reflects the light upward.
  • T: Tubular fluorescent.
  • T3: halogen tubular bulbs such as the rightmost halogen work-light bulb shown in the photos above. This bulb uses an RSC base.
  • VWFL: Very wide flood.
  • WSP: Wide spot.
  • WFL: Wide flood.

Explanation of Color Temperature and CRI for Indoor Lights & Bulbs

Globe bulbs illustrate temperature differences (C) D FriedmanColor temperature and color rendering index (CRI) are two different ways to characterize how colors appear under a light source. At left our photo illustrates that once a lamp is turned on you may observe significant color temperature differences even among bulbs that look physically the same when "off". The two bulbs at right are giving off a warmer, more yellow-orange spectrum light than the two at left.

Color Temperature is expressed in degrees Kelvin, and for incandescent lights equals the temperature of the metal filament. For fluorescent's and other bulbs without filaments, it is the theoretical equivalent temperature.

Lower color temperatures indicate “warmer” light with more yellow and red tones, which complement skin and natural wood finishes.

Higher color temperatures indicate “cooler” light with more blue and green tones, which renders faces harshly and tends to make skin look pale (Table 5-23).

Skin tones look best under lamps rated from 2700K (standard A-bulb) to 3500K and with a CRI over 80. Residential lamps range as high as 7500K for continuous spectrum fluorescents, such as GE’s Chroma 50 or 75. These simulate daylight and are good for detailed work where color accuracy is critical, but they give skin an unflattering greenish tone.

Table Comparing Color Temperatures of Different Bulb Types

Table 5-23: Color Temperatures of common lamps (bulbs) (C) J Wiley, S Bliss

Also see our separate article Color Temperature Bulb Comparisons in which we give photographs and illustrations comparing color temperature differences among light bulb types and in comparison with natural daylight. There we include a more lengthy table of color temperatures and light sources.

Definition of CRI (Color Rendering Index) Scale Rates Accuracy of Lighting from Various Bulb Types

Halogen work light (C) Daniel FriedmanCRI is a rating on a scale of 1 to 100 of how accurately a lamp shows colored objects. The higher the CRI, the closer the colors look to a standard reference.

For incandescent lamps and all others with a color temperature of 5000K or less, the reference is an incandescent or halogen bulb, which are both assigned CRIs of 100.

For lamps with a color temperature of over 5000K, the reference is natural daylight, which also has a CRI of 100.

CRI numbers are best used to compare lamps with color temperatures within about 300K of each other. Colors will look very different under a 3000K lamp and a 6000K lamp with the same CRI.

-- Adapted with permission from Best Practices Guide to Residential Construction.

Define Lumens: a Measures Bulb or Lamp or Light-source Brightness

Light comparison in lumens (C) Daniel Friedman

Lumens is a measure of the amount of light contained within an area or within a defined beam or angle emitted from the light source. Lumens is further defined as the total amount of visible light emitted by a source.

Visible here refers to the light spectrum visible to humans. Some other animals are sensitive to light at ends of the spectrum that humans are not.

... emitted by a source seems funny. If light is not emitted from some source we're not going to see it, right? Well not exactly. There may be ambient light or indirect lighting to complicate matters. So we do talk about light emitted from a particular source so that we can evaluate its output in lumens.

Quantitatively lumens are often defined in luminous flux, at angles in steriradians and measured in candela - terms so unfamiliar to non-engineers that a more familiar practice is to translate lumens roughly into watts.

With an assumption that the light being radiated is in a color that the human eye can best detect (green region at a wavelength of 555nm), then

  • one lumen of visible light represents 1/683 watts, or
  • one watt of visible light represents 683 lumens

More lumens means humans see more light. Many but certainly not all lamp bulb packages indicate the brightness of the bulb (when new, since some bulbs degrade or shift in color temperature with age), in lumens.

Lighting Efficacy (brightness) & Lighting Efficiency

As we explain at LIGHTING, INTERIOR GUIDE, in measuring lighting efficacy, the light output of a lamp per electricity consumed, expressed as lumens per watt. Fluorescent's are three to five times more efficient than standard “A” lamp incandescent's.

And as we note at Lamp & Bulb Types, Indoor, some lamps are more energy-efficient, providing more lumens for the same amount of electricity consumed. Fluorescent's are the most efficient, using up to 70% less energy than an equivalent incandescent bulb (see Table 5-22 in that article).

Watch out: the wattage of a light bulb does not allow you to directly calculate its output in lumens, and equally, lumens of visible light expressed in watts will not translate directly into the rated wattage of light bulbs. So you cannot multiply rated-bulb-watts x 683 to calculate lumens. That's because bulbs are not 100% efficient. Not all of the energy used by the bulb (measured in watts) produces visible light. Instead, much of the energy, varying by bulb type, is dissipated as heat. Some examples:

  • A candle provides about 12 lumens
  • A 60-watt soft light incandescent 120-V light bulb provides about 850 lumens.
  • A halogen T3, RSC-base 100-Watt 120V bulb (Phillips) is rated at 1,600 lumens, not 100 x 683=68,300.
  • A halogen GU-10 50-watt 120-V bulb (GE's Constant Color®) is rated at 400 lumens, not 50 x 683=34,150
  • A halogen MR-16 20-watt 12-V bulb (GE's edison® 20, on the package, does not state the light output in lumens
  • LED bulb brigtness in lumens and energy costs are at our Table of Current LED Bulb Prices & Features.

-- Adapted with permission from Best Practices Guide to Residential Construction.

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