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Brightness & Illumination 

    Lights Are Us's LED Academy: Light Bulb Brightness Explained

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Various Definitions of LED Brightness: lux, lumen and watt

In this lesson we are going to define some of the many terms used in light brightness such as watt, lumen, and lux. 
Here we will discuss:
  • measuring the amount of light produced from an LED light source
  • measuring the amount of light we see from an LED light source
  • measuring the amount of usable light produced from an LED light source

This discussion is not a rigorous scientific analysis, it is intended to offer an understanding of a few of the various terms used related to LED light bulb brightness. 

Watt as a measure of LED brightness

A measure of brightness used in the past was the wattage of a light. With more efficient lighting products like CFL and LEDs, use of the watt is no longer an accurate means of determining brightness across multiple lamp technologies. For example: a 75 Watt incandescent bulb, 18 watt CFL and a 9 watt LED may all produce the same amount of usable light. Obviously watt is not longer a viable means to measure the brightness of a light source. 

LED Lumen as a measure of brightness

The LED lumen measures the total amount of visible light from a light source. Unfortunately some light may be used to light areas not even visible to the viewer. Such as the lighting of the inside of a fixture. This is why the measure of the light found on the projected surface is often a much better measure of applicable light. LED lumens often times are less than the lumen measure of an other light technology for the same amount of brightness on the working surface. This is due to the directed nature of LED packaging. This direction of the LED lumen results in greater use of the available light. 

LED Lux as a measure of brightness

The measure of the amount of visible light on a surface, like the lux, is a good way to determine the amount of "usable" light created by a light source. 

LED Lux as a measure of brightness

The measure of the amount of visible light on a surface, like the lux, is a good way to determine the amount of "usable" light created by a light source. 
Light Measurement Definition Form of Measure
Radiant Flux the total power of light: visible and non-visible light watt (W)
Luminous Flux or Luminous Power the perceived power of light adjusted to reflect the varying sensitivity of the human eye to different wavelengths of light lumen (lm)
Luminous Intensity the amount of lumen on a square meter lux (lx)
Luminous Efficiency the amount of visible light produced per each watt consumed lumen/watt (lm/W)
The radiant flux is the total amount of light generated, this includes light that is not visible to the naked eye like infrared and ultraviolet. 
The luminous flux is an adjustment to the measurement of radiant flux that measures only that light perceived by the human eye. The LED lumen (Lm) is a measure of the amount of LED light produced that we can potentially see. 
The luminous intensity is an adjustment to the luminous flux that measures the amount of light on a surface. Think of this as the usable light. 
When purchasing LED light bulbs you may see that the lumen listed on the LED does not match that of an incandescent, but the lamps offer the same about of light on your desk or table. This is because the light from LEDs are often "directed light" where an incandescent light shines light in all directions: only a part of which is used to light up what you are intending. 
When purchasing light bulbs the lumen is one measure to determine relative brightness, however use of the lux gives you a measure of the light hitting the surfaces you are trying to light. 
When choosing a lightbulb, determine the appropriate lux or lumen required and then select that bulb with the fewest watts. Lower wattage means lower electricity bills. Checking LED lumens directly against traditional bulb lumens is only appropriate under certain lighting conditions and certain light bulb shapes and fixture designs.

Light Bulb Base Type

     

Lights Are Us's LED University: Bulb Bases and Sockets Explained

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In this lesson of Lights Are Us's LED Academy we discuss the naming conventions of LED light bulb bases and light bulb sockets. Details of several types of bases and light sockets are shown in diagrams with dimensions and names. 

Naming Conventions of Light Bulb Sockets and Base Types

Light bulb bases and sockets are normally defined by a letter-number-letter format, with the last letter optional. The first letter designates the shape or form of the base, the numbers represent either the width of the base or the distance between the pins. The second letter designates the number of pins or contacts on the lamp. The numbers are normally in millimeters. LED light bulb sockets and bases are manufactured to the same standards as halogen, incandescent and other traditional lights. 

Light Bulb Beam Angle 

By way of example a standard USA screw-in incandescent bulb has a base type of E26. E stands for Edison screw-in and the 26 means that the base is 26 millimeters. E27 is the European standard screw-in size. (note: Lights Are Us part numbers that contain 'E27' sold in North America will fit E26 sockets and in many cases support voltages from 85VAC to 220VAC) 
LED light bulbs and LED lamps use the same socket designations as traditional light bulbs. Retrofit Solid State Lights (SSL) that use LEDs or OLEDs are normally designed to be compatible with existing sockets. 
Light Bulb Base and Socket Shape Types
  • B Bayonet Collar Base
  • E Edison Screw Light Base
  • F Single Pin Type Base
  • G Multiple Pin Type Light Bulb Base
  • K Cable Connections
  • P Pre-focused Light Base
  • R Recessed Contact(s) Base
  • S Shell-type Light Bulb Base
  • T Telephone Slide Base
  • W Wedge Base
  • X Special Type Lightbulb Base

Lamp Number of Pin or Contacts
  • s Single Pin
  • d Double or Bi-Pin Base Type
  • t Triple Pin Base or Tri-Pin Base or 3 Pin Base
  • q Quadruple Pin Base or 4 Pin Base

Bulb Type Details

B or Bayonet light bulb base and sockets

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LED light bulb bayonet base types. 
Examples of these base types include: BA75, BA95, BA150, BAY150, BA155, BA220 
Click on image to enlarge.

Bi-pin and G sockets and bases

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LED light bulb bi-pin base types. 
Examples of LED bipin base types include: G4, G5, GU5.3, GU10, G13, T-1/2, T-3/4, T-1, T-1 1/4, T-1 3/4. 
For more information on G type bases see G below. 
Click on image to enlarge.

E or Edison screw-in sockets and bases

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Screw-in bases, also known as Edison bases and light bulb sockets are used through out the world. 
The naming conventions include terms like medium base and candelabra base. Often they are referred to with a letter-number designation that starts with an "E" followed by the number of millimeters in diameter of the base. If your base ends in a "d" this indicates a double contact base, this is typically used for 3-way bulbs. 
Typically North American 120VAC bases and 240VAC bases differ by only a millimeter and carry the same full name in each country. Many Lights Are Us bulbs support both 120VAC and 240VAC, check specifications for the bulb to determine if the bulb supports 240VAC if your application requires that. 
Click on image to enlarge. 
"E" or Edison base types, sizes and names 
Base Number Diameter Base or Socket Name
E5 5mm Lilliput Edison Screw Base
E10 10mm Miniature Edison Screw Base
E11 11mm Mini-Candelabra Edison Screw Base
     
E14 14mm Small Edison Screw Base (supports 240V)
E17 17mm Intermediate Edison Screw Base
E26 26mm Medium Edison Screw Base
     
E39 39mm Mogul or Giant Edison Screw Base
E40 40mm Mogul or Giant Edison Screw Base (supports 240VAC)

F or Flange light bulb base and sockets

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LED light bulb flange base types. 
LED flanged bases include base types like: micro-midget flanged base, midget flanged, miniature midget flanged, sub-midget flanged, and special-midget flanged base types. These LED light bulb types are used in automotive and electronic device lighting applications. 
Click on image to enlarge.

G or Bi-pin light bulb base and sockets

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The "G" base type of lamp and light bulb is used to designate a "pinned" base. This can include several pin types and different numbers of pins. 


Designation is by letter(s)-numbers-optional letter: The first letters include "G" followed by an optional U, X, Y or Z. Next is a number that designates the number of millimeters between the center of each pin. Finally the optional final letter designates the number of pins, no letter implies 2 pins as does a d for double. Pin number designations include: s : Single, d : Double, t : Triple for 3 pins and q : Quadruple for 4 pins. 
Examples include: GU10 base type, G24q base type, or for T8 tubes G13 bi-pin. 


Click on image to enlarge. 


Type Pin to pin distance Pin Diameter Typical Bulbs that use this base
G4 4mm 0.65-0.75mm MR11 and other small halogens of 5/10/20 watt and 6/12 volt
GU4 4mm 0.95-1.05mm  
GY4 4mm 0.65-0.75mm  
GZ4 4mm 0.95-1.05mm  
G5 5mm   T4 and T5 fluorescent tubes
G5.4 GU5.3 GX5.3 GY5.3 5.33 mm 1.47-1.65mm MR16 and other small bulbs typically using 12/24 volts
G6.35 GX6.35 GY6.35 6.35 mm 0.95-1.3mm  
G8 8mm    
G9 9mm    
GU10 10mm   bulbs using twist-lock bi-pin base
       
G23 23mm 2mm  
GU24 24mm   2 and 4 pin bases with center key
GX53 53mm   used with puck shaped lamps typically twist-lock

K or Cable connected lights and lamps


Lights Are Us uses the designation of K to indicate that a cable is the power connection for a lamp. This designation is Lights Are Us product specific. So where you see a K used in a base type location in a part number. You can assume that the product is a wired connection to power.

P or Pre-focused lamp base and sockets

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LED light bulb pre-focus base types: S.C. Prefocus and D.C. Prefocus 
Click on image to enlarge.

R or Recessed lamp base and sockets

S or Slide light bulb base and sockets

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LED light bulb slide base types. 
Examples of LED slide base types like Slide #1. 
Click on image to enlarge.

W or Wedge light bulb base and sockets

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LED light bulb wedge base types. 
Examples of LED Wedge base types include: D.F Wedge and S.F. Wedge sockets. 
Click on image to enlarge.

Light Bulb Measurement 

    

Lights Are Us's LED University: Light Bulb Beam Angle Explained

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Definition of Light Bulb Beam Angle


The beam angle is the degree of width that light emanates from a light source. Specifically: The angle between those points on opposite sides of the beam axis where the intensity drops to 50% of maximum. 
LED lighting like most lights come with a variety of descriptions for the size of the area illuminated by the light bulb. Examples include LED flood light, LED spot light, narrow beam LED light, and wide beam LED strip lights. Each is a way of stating LED beam angle. Typically a narrow beam angle is a 'spot' of light and a broader beam angle 'floods' an area with light, called a flood light. LED beam angles are not used consistently by light bulb manufacturers. The information below is a summery of uses of the term beam angle. Please note that not all lamp shapes use the same terms. 
Click on picture to enlarge. 

Names and Examples of Light Bulb Beam Angles

Description Code Typical MR16 Beam Angles Typical PAR Beam Angles
Very narrow spot VNSP <7 degrees <15 degrees
Narrow spot NSP 5-15 degrees 15-30 degrees
Spot SP

Lights Are Us LED University: Color Temperature & Kelvin Explained

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Definition of LED Color Temperature

 

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