Light Bulb Shape, Base and Filament Types

lighting technologies updating

Light bulbs come in a fascinating variety of shapes, bases, and filaments, each designed to serve specific lighting needs and select fixtures. The base of a light bulb is equally important, as it determines how the bulb connects to the electrical supply. Filaments, the heart of incandescent bulbs, also vary, with materials ranging from tungsten to carbon, shaped to maximize or limit efficiency and life hours. These diverse components allow light bulbs to illuminate spaces effectively, catering to the vast needs of residential, commercial, and industrial applications.

The code number of a filament consists of a letter or letters to indicate how the wire is coiled. A number followed by the letter indicates the arrangement of the filament on the supports. The letter “C” is commonly used indicating “Coil” type filament.

The code number of a bulb consists of a letter or letters followed by a number. The letter indicates the shape of the bulb and the number relates to the diameter of the bulb in eighths of an inch. The mosts commonly used household bulb is the A-19. The bulb is “A” type and the diameter would be 23/8″. A 65BR40 is a 65 watt reflector 5″ in diameter.

Bulb Shapes, Bases, & Filaments

Every traditional bulb shape below is now available in LED lighting, combining classic designs with energy-efficient, long-lasting LED technology with an improved spectrum of light.

light bulb shapes

A Series Light Bulbs
The "A" in A Series stands for Arbitrary, the most common and recognizable bulb shape. These bulbs have a pear-like shape, tapering down to the base, and are used in a wide range of applications, from residential lighting to commercial settings. The A19 bulb, for example, is a standard size used in many household lamps. These bulbs provide a wide, general light spread, making them versatile for various settings.

PS Series Light Bulbs
PS Series bulbs, where "PS" stands for Postscript or Pear-Shape, are elongated bulbs that often resemble the shape of a teardrop. They are larger and longer than A Series bulbs, designed to distribute light over a wider area with their extended shape. PS bulbs are commonly used in outdoor lighting fixtures, floodlights, and in areas where a more concentrated light is needed over a long distance.

B Series Light Bulbs
The B Series, with "B" standing for Blunt tip, resemble a flame or a torpedo shape, often used in decorative fixtures. The blunt, rounded tip gives these bulbs a unique appearance, making them ideal for chandeliers, wall sconces, and other fixtures where the bulb is visible and aesthetics are important. 

C Series Light Bulbs
C Series bulbs, where "C" stands for Conical or Candle, are shaped like a cone or a candle flame, tapering to a pointed tip. These bulbs are designed primarily for decorative use, perfect for candle-style chandeliers, Christmas lights, and night lights. The shape of C Series bulbs is not just for aesthetics; it also helps in directing light, making them suitable for accent lighting.

decorative bulbs shapes

CA Series Light Bulbs
The CA Series, standing for Candle Angular, features bulbs with a decorative, angular shape that mimics a flame or bent tip, reminiscent of a candle. These bulbs are favored in settings where the bulb itself is a focal point of decor, such as in chandeliers, wall sconces, and decorative lamps. Their design enhances the visual appeal of the lighting fixture that enhances the ambiance of any space.

RP Series Light Bulbs
RP Series bulbs, Reflective Parabolic design, are engineered for precision lighting. These bulbs include a reflective coating on their interior surface, focusing light into a directed beam. This makes them ideal for applications requiring targeted illumination, such as spotlights, track lighting, and outdoor floodlights. The RP Series is perfect for highlighting specific areas or objects.

S Series Light Bulbs
The S Series bulbs are known for their Straight-sided shapes, often employed in various applications where a simple, cylindrical form is desired. These bulbs can serve both functional and decorative purposes, including use in outdoor lighting, commercial signage, and accent lighting. Their straightforward design allows for uniform light distribution in a wide array of settings, making them a versatile choice for many lighting needs.

F Series Light Bulbs
F Series bulbs, or Flame-shaped bulbs, are designed to emulate the flicker and shape of an actual flame. These bulbs offer a decorative touch with their unique form, ideal for creating a cozy, inviting atmosphere in residential settings or adding a vintage charm to lighting fixtures. Commonly used in open lamps, wall sconces, and chandeliers, F Series bulbs provide ambient lighting with a decorative flair.

Prism-shaped Light Bulbs
Prism-shaped bulbs stand out for their ability to diffuse light evenly while minimizing glare. Their surface, etched or molded with facets like a prism, scatters light across a broader area, ensuring a uniform distribution of light.

Globe and Tubular bulb shapes

G Series Light Bulbs
The G Series light bulbs, where "G" stands for Globe, are characterized by their round, spherical shape. G Series bulbs are often found in bathroom vanities, pendant lights, and decorative fixtures where the bulb itself is an integral part of the fixture's aesthetic. Their large surface area allows for an even distribution of light.

T Series Light Bulbs
The T Series, with "T" standing for Tubular, features bulbs that are elongated and cylindrical in shape. These bulbs are designed for specialized applications that require a focused, linear spread of light. T Series bulbs are commonly used in picture lights, under-cabinet lighting, and in certain types of commercial and industrial equipment. Their narrow form factor makes them particularly suited for fixtures where a compact, directional light source is needed. T Series bulbs can also be found in refrigerators, ovens, and other appliances due to their ability to fit in tight spaces and provide adequate illumination.

CFL bulbs shapes

Linestra Bulbs
Linestra bulbs are distinctive for their long, tubular shape, providing a soft, diffused light ideal for use in vanity mirrors, architectural lighting, and decorative applications where a continuous line of light is desired. They offer a direct, glare-free illumination, making them perfect for settings where both ambiance and functionality are important. The sleek design of Linestra bulbs lends a modern aesthetic to any space, blending seamlessly with contemporary decor.

Linear Fluorescent Bulbs
Linear Fluorescent bulbs are a popular choice for commercial, industrial, and residential lighting. These tubes, typically T-shaped with varying sizes indicated by numbers (such as T8, T12), emit a bright, uniform light across a wide area. They are often used in office buildings, schools, and retail spaces for general lighting purposes. 

Compact Fluorescent Bulbs (CFLs)
Compact Fluorescent bulbs, or CFLs, are designed to offer the energy efficiency of fluorescent lighting in a more compact, easy-to-use form factor. These bulbs are characterized by their twisted or folded shape, which allows them to fit into standard light bulb sockets. 

reflector bulb shapes

R Series Light Bulbs
The R Series bulbs, with "R" standing for Reflector, are characterized by their wide, reflective surface designed to direct light in a specific pattern. These bulbs are commonly used in recessed lighting fixtures, floodlights, and spotlights. The shape of the bulb helps in distributing the light over a broad area, making them ideal for general lighting purposes in both residential and commercial settings. The reflective interior enhances the efficiency of light output, directing it where it's most needed.

MR Series Light Bulbs
The MR Series, where "MR" stands for Multifaceted Reflector, features bulbs with a smaller diameter than the R Series and is designed with precision lighting in mind. These bulbs have a tight, controlled beam of light, making them perfect for task lighting, accent lighting, and display lighting. The multifaceted interior of the bulb reflects light in multiple directions, resulting in a focused and intense beam of light. MR bulbs are often used in track lighting, landscape lighting, and retail display cases.

BR Series Light Bulbs
BR Series bulbs, meaning Bulged Reflector, are similar to the R Series but with a bulged shape that allows for a wider light distribution. The wide beam angle of BR bulbs makes them suitable for use in overhead lighting fixtures where a broad, even light is desired. The design of the BR bulb minimizes glare and shadows, providing a comfortable, evenly lit environment.

par reflector shapes

PAR Series Light Bulbs
The PAR Series, standing for Parabolic Aluminized Reflector, bulbs are engineered for accurate and focused light projection. These bulbs are characterized by their parabolic shape, which includes a reflective coating inside the bulb that directs the light through a lens at the front of the bulb. This design allows for a controlled and precise beam of light, ideal for spotlighting and flood lighting applications. PAR bulbs are commonly used in theatrical lighting, concert lighting, and in retail to highlight merchandise. They are also popular in outdoor settings for security lighting and landscape illumination. The series includes various sizes (e.g., PAR16, PAR20, PAR30, PAR38), indicating the diameter of the bulb, which allows users to select the appropriate size for their specific lighting needs.

Specialty Shaped Light Bulbs
Specialty-shaped light bulbs encompass a wide range of unique designs tailored for specific purposes or aesthetic appeals. This category includes bulbs with unconventional shapes, sizes, or functionalities not typically found in standard lighting applications. such as ultraviolet bulbs for disinfection, infrared bulbs. 

HID Bulb Shapes

BT Series Light Bulbs
The BT Series, where "BT" stands for Bulged Tapered, features bulbs that are characterized by their bulged base and tapered neck. This unique shape allows for a wider distribution of light compared to standard bulbs, making BT Series bulbs suitable for areas where broad, diffused lighting is needed. They are commonly used in industrial settings, large open spaces, and outdoor lighting fixtures where effective illumination over a large area is required. The design of the BT bulb helps in reducing shadows and providing uniform light coverage.

E Series Light Bulbs
The E Series light bulbs are distinguished not by their shape but rather by their base type. The "E" typically refers to Edison Screw, a standard socket for light bulbs. This series encompasses various bulb shapes and sizes that utilize the Edison screw base. The versatility of the E Series lies in its compatibility with a wide range of lighting fixtures, making it a universal choice for both residential and commercial lighting applications.

ED Series Light Bulbs
The ED Series, with "ED" indicating Elliptical Dimpled, consists of bulbs that have an elliptical shape and a textured surface to diffuse light more evenly. This series is often used in outdoor lighting fixtures and street lamps. The dimpled design helps in spreading the light over a wider area while minimizing glare, making it an ideal choice for public and commercial spaces where safety and comfort are priorities. The ED Series bulbs are known for their durability and efficiency in outdoor environments.

AR Series Light Bulbs
The AR Series, standing for Aluminum Reflector, includes bulbs designed specifically for precise light control. These bulbs are typically used in track lighting, retail display lighting, and other applications where directed light is necessary. The AR Series bulbs have a mirrored aluminum coating on the inside of the bulb that reflects light forward, creating a focused beam. This allows for targeted illumination of specific areas or objects, enhancing visibility and highlighting details. AR bulbs are commonly available in different beam angles to accommodate various lighting needs.

reflector bulb shapes
Plug In CFL base types

Bi-pin Bases
Bi-pin bases are used in a wide range of light bulbs, from small halogen lamps to certain types of LED bulbs. This base type features two metal pins protruding from the bottom of the bulb, which insert into matching sockets. The distance between the pins can vary, leading to different standards (such as G4, G9, GU10, and GU24), which are determined by the pin spacing in millimeters. Bi-pin bases provide a secure electrical connection and are commonly used in specialized lighting fixtures like under-cabinet lighting, desk lamps, and certain types of track and recessed lighting. Their compact size makes bi-pin base bulbs an excellent choice for applications where space is limited, and precise directional lighting is required.

Fluorescent Bases
Fluorescent pin bases are specifically designed for fluorescent tube lights and compact fluorescent lamps (CFLs). These bases feature two or more pins that slot into corresponding fixtures. For tube lights, common bases include the T8 and T12, which refer to the diameter of the tube in eighths of an inch and have a pin base at each end of the tube. CFLs use a G24 or GX23 base, among others, with multiple pins arranged in specific configurations to match their fixtures.

more light bulb shapes
specialty light bulb base types

The filament in a light bulb is crucial for its operation, especially in incandescent and halogen bulbs, where the filament heats up and emits light. Over the years, various filament shapes have been developed to optimize light output, efficiency, and bulb life hours. Here are some of the different filament shapes that have been used in light bulbs:

Squirrel Cage Filament
One of the most iconic filament designs, the squirrel cage filament, features a series of vertical wires supported by horizontal crossbars, resembling the wheel of a squirrel cage. This design is not only aesthetically pleasing but also provides a distinctive, warm glow. It's commonly found in vintage or Edison-style bulbs, where the filament is a key part of the bulb's decorative appeal.

Coil or Spiral Filament
The coil filament, also known as a spiral filament, involves winding the tungsten wire into a tight coil. This design increases the length of the filament in a compact space, improving the efficiency of the bulb by providing more surface area for light emission. Coiled filaments are common in both traditional incandescent bulbs and halogen lamps.

Double Coil or Coiled Coil Filament
An advancement of the coil filament, the double coil or coiled coil filament involves an additional winding process where the already coiled tungsten wire is wound once again into a larger coil. This design further enhances the light output and efficiency of the bulb, as well as extending its lifespan by reducing the rate of tungsten evaporation.

Loop Filament
Loop filaments feature the tungsten wire shaped into one or more loops inside the bulb. This simple yet effective design is often used in decorative bulbs and antique-style lighting, where the looped filament adds to the visual interest of the bulb.

Straight Filament
Straight filaments are exactly as they sound: a straightforward, uncoiled strand of tungsten wire that spans the length of the bulb. This design is among the earliest filament shapes and is less common today due to its lower efficiency compared to coiled designs. However, straight filaments may still be found in specific applications where simplicity and a retro look are desired.

Zigzag or Crisscross Filament
Zigzag or crisscross filaments feature a tungsten wire that is bent back and forth in a zigzag or crisscross pattern. This design allows for a larger filament surface area, improving brightness and efficiency. It also adds an attractive visual element, making it popular in decorative and vintage-style bulbs.

lumen master closing image of tom Enright



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