Choosing the right light bulb can be confusing with all of the different numbers and letters used to describe bulbs. You need to know about the various types and styles of bulbs when choosing the right one for a specific purpose. Bulbs such as the R20 and the PAR20 share some traits, but their differences will make one better than the another for specific applications.
PAR stands for parabolic aluminized reflector. This is a type of coating that is used on the lower portion of a light bulb to direct the light out the end of the light bulb. It provides a more focused beam of light, enabling it to be used as a spotlight or accent light instead of a general room light. The "R" alone indicates a reflective coating, but it does not provide the compact beam of the PAR.
The designation "20" on a light bulb indicates the size of the bulb. Light bulbs are measured in eighths of an inch, so a bulb designated as a size 20 measures 20 eighths of an inch, or 2 1/2 inches, across at the largest point. This means that R20 and PAR20 bulbs are the same size. This doesn't have anything to do with the base of the bulb, which is a standard size and should fit any standard socket.
Three types of lighting methods can be used for either R20 or PAR20 bulbs. The first type is the incandescent bulb, in which a filament inside the bulb heats up and makes light when the bulb is in use. The second type is the halogen light, which is a form of incandescent light, but with a difference. A halogen bulb has a small inner bulb filled with halogen gas encased within the larger bulb. The third type is a light emitting diode, or LED. This light is cool in operation, lasts a long time, and uses little energy.
An R20 bulb is commonly used for regular room lighting, or to provide soft illumination for a specific area. The light emitted by an R20 does not have defined edges but instead has a bright central area, becoming more diffused and dimmer as it spreads out. A PAR20 bulb is best used when a crisp, focused beam is desired. This type of bulb works well to illuminate artwork or specific points where diffuse lighting is not wanted. The reflective coating directs the light to a specific, targeted area, resulting in a more intense area of lighting with clearly defined edges.