Naming Conventions for Light Bulb Shapes
Definition of Light Bulb Beam Angle
The beam angle is the degree of width that light emits from a light source. In specific terms this is the angle between the opposing points on the beam axis where the intensity drops to 50% of its maximum.
LED lamps come with a variety of descriptions for the beam angle. A wide beam angle ‘floods’ an area with light and is called a flood light where as a narrow beam angle is a ‘spot’ of light, hence spot light. LED lamp beam angles are not used consistently by light bulb manufacturers. Not all lamps use the same terms.
Names and Examples of Light Bulb Beam Angles
Source:
http://www.whichledlight.com/led-beamangle