Lighting controls and influences so much of our lives, yet few people put much thought into their lighting, let alone know the differences between all the types and shapes of light bulbs!

Lighting is a powerful tool whose full effect is felt most if you know how, when, and where to use it! 

So while we usually focus primarily on lighting and wellness, we realized more of you might need guidance on how to best use these tools efficiently! 

To understand light bulbs, you should first understand these essential three components: 

1. Lighting Technology, or the way the bulb uses electricity to create visible light. The most common technologies are incandescent, halogen, LED, and fluorescent.  

2. Bulb Shape/Type determines how the light is distributed. Every bulb shape has a recommended usage or fixture to be used in. For example, flood-type bulbs are best for recessed ceiling fixtures; standard light bulbs for desk and floor lamps. Bulb Base determines how the bulb screws or plugs into a socket. 

3. Color Temperature is used to describe a lights visual appearance and whiteness. Most range from the warmer 2700K to the cooler, "bluer" 6500K. 

 

 Let's jump in! 

 

The different light technologies.

A few standard technologies are used in household lightbulbs, so let's get into each. Remember, this is how a bulb uses electricity to create visible light, and the most common technologies are incandescent, halogen, LED, and fluorescent. 

Incandescent 

We start with the lighting technology used for the first-ever light bulb - the incandescent light bulb. When you think of an Edison bulb with a glowing filament inside, that is incandescent.

Incandescent bulbs - in addition to the "enhanced" halogen versions we'll get into next - are what we like to call "analog" light sources. They also happen to be what many believe to be the healthiest, most natural type of lighting technology. Interestingly, they're most similar to natural sunlight, which is also an incandescent light source.

How it works: filament heats up to produce thermal energy (infrared) and visible light.

What it looks like: Warm and natural, though most give off amber or yellow light: most incandescents fall around 2700K to 3000K in color temperature. Some, like Chromalux®, are tuned a bit whiter and purer at 3700K or 4200K. We'll learn more about color temperature below. 

 

Halogen 

Next up, we have the halogen light bulb, which - as mentioned above - is just an enhanced version of an incandescent light bulb.

How it works:  Instead of a filament enclosed in a glass shell, it is first encapsulated in a quartz capsule filled with a halogen gas (bromine or iodine). This allows for a halogen-cycle chemical reaction which allows the filament to burn hotter, creating a brighter light with a whiter color temperature than a typical incandescent using only a tungsten filament.

What it looks like: Pure and white.

 

Fluorescent 

Now, onto creating light through fluorescence. Whether linear tube fluorescent lights in offices or the compact fluorescent lamps (CFL) with the curly tubes for regular lamps - these types use fluorescence.

How it works: A glass tube coated with phosphor powder is central to fluorescence. Inside the tube is a bit of mercury and inert gas. There are two electrodes at each end of the tube. An electric current in the gas excites mercury vapor, producing ultraviolet light, which is then translated to visible light by the phosphor coating in the tube. 

What it looks like: Manufacturers can vary the color of the light by using different combinations of phosphors. As a result, you can find fluorescents in all different color temperatures; though bright, daylight white fluorescents are the most common variety.

LED

How it works: LEDs, or Light Emitting Diodes, are a light source that uses semiconductors. 

What it looks like: anything! LED are customizable light sources, so they can be made to any specification by changing the diode arrangement and type. 

 

Now, let's get into the shapes of light bulbs.

While there are many bulb shapes, we'll go over the most commonly found ones and the shapes we do carry to help you choose accordingly.

Remember, the shape of a bulb determines how it shines and disperses its light, and every shape has a usage function: i.e., an intended fixture to be used in!

For example, don't put standard "A" shape light bulbs (more on that below) in recessed ceiling light fixtures - the light would get "lost" inside your fixture and not be of much use as a light source! Instead, only use the recommended shape/type of bulb for each fixture (or lamp) in your home. 

 

Standard bulbs - A 

The 'A'-shape light bulbs are what you think of when you think of a typical household light bulb: an upside-down pear-shaped bulb that gives off light omnidirectionally (360 degrees).

The numbers after the "A" determine the bulb's diameter at its widest part in 1/8ths of an inch.

The standard A19 bulb, for example, has a diameter of 2.375'', or 19 divided by 8.

The next step up in size is the A21, which has a diameter of 2.6'', or 21 divided by 8.

A19 = standard household bulb with a diameter (at its widest point) of 2.4'' and a length of 4.25''

A21= standard household bulb with a diameter (at its widest point) of 2.6'' and a length of 5.25''

The part of the bulb that you screw into a lamp or fixture is called the base. Standard light bulbs will always use a so-called E26 (medium) screw-in base. 

 

Flood bulbs (Reflectors) - R

Next up is the Reflector flood lamp, or R-shaped lamp. The "R" stands for reflector and refers to how the light is reflected inside the bulb. 

Whereas our preceding standard A-shape bulbs give off light in all directions, making them perfect for your standard and typical desk, table, or floor lamp,  reflectors are "directional" lights, with an inner reflector accentuating the light beam downward. R-shape reflector floods are most commonly used in overhead recessed can light fixtures but can also be used in tracks. 

As before, the digits after the letter refer to how wide the bulb is at its widest diameter. 

In order of smallest to largest, then:

R20 = flood-shaped bulb with a diameter of 2.5'' and a length of 3.8''.  Used in recessed can fixtures with a diameter of 3''- 3.5''

R25 = flood-shaped bulb with a diameter of 3.1'' and a length of 4.3''.  Used in recessed can fixtures with a diameter of 3.5''-4''

R30 = flood-shaped bulb with a diameter of 3.75'' and a length of 5.25''. Used in recessed can fixtures with a diameter of 5''- 6''

R40 = flood-shaped bulb with a diameter of 5'' and a length of 6.75''. Used in recessed can fixtures with a diameter of 6''

Choosing the right size R-style bulb is a matter of measuring the diameter and depth of your recessed light fixture. 

Generally speaking:  

3'' diameter = R20

4-5'' diameter = R25/R30

6'' diameter = R40

All the above reflector-shape light bulbs will always use a so-called E26 (medium) screw-in base.

 

PAR Lamps (spotlights) 

Another great light to be used in recessed fixtures, the beam on PAR lamps will be tighter with a more defined edge (more of a spotlight) than Reflector R lamps, which have a wider "flood" effect.

PAR20= spot lamp with a diameter of 2.5''

PAR30= narrow flood lamp with a diameter of 3.75''

PAR38=narrow flood lamp with a diameter of 4.75''

Choosing the right size PAR-style bulb is a matter of measuring the diameter and depth of your recessed light fixture. 

Generally speaking:  

3'' diameter = PAR20

4-5'' diameter = PAR30

6'' diameter = PAR38

All reflector-shape light bulbs will always use a so-called E26 (medium) screw-in base.

 

B10 - Candelabra (Candle) Bulbs 

These bulbs resemble the shapes of candle flames and are most commonly used in candelabra fixtures such as chandeliers and sconces. 

While the shape is that of a candle flame, this differs from the base, which can either be your standard medium E26 screw-in base, or the skinnier E12 candelabra base, which is commonly used in chandelier and sconce fixtures. 

 

Globe bulbs - G 

Commonly used in bathroom vanity fixtures or for decorative purposes, globe-shaped bulbs have a perfectly spherical shape and are available in either the smaller E12 candelabra base, or E26 medium base.

Chromalux® carries two globe bulbs:

G25 - globe-shaped bulb with a 3.125'' diameter and an E26 medium base

G16 ½ - globe-shaped bulb with a 2'' diameter and an E12 candelabra base

 

MR16 (Multifaced reflector)

The MR bulb is a small spot-type light bulb for directional, accent lighting used primarily in track lighting. The most popular are MR16, which are 2 inches in diameter.

These bulbs are commonly found with two bases: GU 5.3 (Bi-pin) for low-voltage track fixtures, or GU10 (twist and lock), for line voltage fixtures.

 

Lighting Metrics: describing visible light

Now that we've got the technology and shape of light bulbs down, let's learn more about the different metrics used to quantify the visible light they produce. In other words, the color appearance of the light (how white the light is), brightness, and how well it depicts color. 

Color temperature

Color temperature is a measure used to describe a light source's visual appearance and whiteness. Just like natural sunlight has many shades, artificial lighting also comes in many shades of white. These are a light's color temperatures, represented as degrees Kelvin (˚K). 

The color temperature range of most light bulbs falls between 2700K and 6500K. 

The lower the Kelvin temperature, the "warmer" or more yellow the light, getting "cooler" and whiter as the Kelvin temperature increases. 

Therefore, of the above 2700K-6500K range, 2700K represents a warmer light, and 6500K, a bright white light. 

To learn more: check out this article

Brightness (lumens)

The brightness of the visible light emitted by a bulb. While wattage describes a bulb's energy draw, lumen count better describes how much light a bulb emits or how bright the bulb is. 

Wattage

The energy draw of a light bulb. Whereas wattage was used as a reference point for brightness in the past, that is no longer the case with new energy-efficient lighting technologies. Nowadays, use lumen count instead to determine how bright a light source will be. 

Color rendering index (CRI)

CRI is a measure on a scale of 1 to 100 of how accurately a light source shows colors compared to natural sunlight (with a CRI rating of 100).

A light bulb with a CRI above 90 is considered good, and above 95, excellent for color vibrancy and a more natural-looking interior. Stay away from CRI ratings below 85, which have a dulling effect on surroundings. 

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