When you are selecting a light fixture for your area, you has to consider the distance that the light fixture’s light have to reach the area that you want to illuminate, and the beam angle of that light fixture. Many people will focus on the lumen count of the different light fixtures, but the lumen count is only a measurement of the total amount of visible light that the light fixture will emit. The total light output wont help you to determine the distance that the light will travel.
Instead, if the light fixture emit a narrow beam angle, it will emit most of its lumens into a small area, and allow those lights to travel further. Conversely, if the light fixture emit a wide beam angle, it will spread most of its lumens into a larger area, and the light intensity will fade more quick with distance. Regardless of the different types of light fixtures, the relationship between the lumens of that light fixture and the beam angle of that light fixture will remain the same.
How Lumens and Beam Angle Affect Light Reach
For instance, a flashlight that emit 1,000 lumens with a narrow beam will be able to identify an object that is hundreds of feet away, but a flashlight that emit 1,000 lumens with a 120-degree beam will only be able to reach the end of a driveway. The relationship between light fixtures like security lights, pathway lights, reading lamps, and projectors will follow this same principle; each type of light fixture will have different requirements with regard to its lumen and beam angle specifications. The distance that a light can travel can be calculated using a specific mathematical process.
The process involves first converting the lumens of the light source to its peak intensity according to the beam angle of the light fixture, then applying the inverse square law to that light source. The beam angle will have a major impact on the distance that the light can travel; a narrow beam angle will allow the light to travel further than a wide beam angle with the same lumen count. For instance, halving the beam angle of a light source will quadruple the throw distance of the light source; this is why a narrow beam light source can travel further than a bright flood light of the same lumen count.
Many outdoor light fixtures will require you to make a decision of the relationship between the reach of the light source and the coverage that it will provide. For instance, pathway lights have to travel a short distance to reach the path that you travel down, so the beam angle of pathway lights is relatively wide and the lumen count is relatively low. Perimeter security lights has to travel a relatively long distance to reach the perimeter of the property to make an intruder or animal recognizable, so the beam angle is narrow and the lumen count is relatively high.
Indoor lights will follow the same principles as outdoor lights with respect to the area that they must illuminate; desk lights do not need to emit a high lumen count because the light only needs to travel a few feet into the area of the workbench or desk, but a garage light fixture will need a higher lumen count to provide even illumination to the much larger area. Projectors will also follow these same rules regarding the physics of light, but there is an additional complication regarding the distance of the throw of the image that a projector will reflect. As the throw distance of the projector increase, the size of the image that the projector forms increase, but the brightness of that image decrease.
A 2,000-lumen projector may reflect an excellent image onto a screen that is located ten feet from the projector in a very dark room, but the same projector may reflect a much dimmer image onto a screen that is located twenty feet from the projector in a room that also receives daylight illumination. Consequently, many individuals that purchase a projector will focus upon the lumen count of that projector, but will become confused as to why the projector image appear to be washed out. Common mistakes with light fixtures can include two different scenarios.
For instance, many individuals will purchase a light fixture with a higher lumen count than their previous fixture, but discover that the beam angle of the new fixture causes the light to either be too bright in one area or not reach as far as with their previous fixture. Additionally, individuals may purchase a fixture with the highest lumen count in order to provide security lighting for there yard, but they end up with a bright spot directly under the light fixture while the remainder of their yard remains in the dark. In order to select the correct light fixture for your desired location, you must first determine the distance that the light fixture should travel and the area that it should illuminate.
Based off these two factor, you can select the lumen and beam angle that will provide such distance and illumination of the area. Following these steps will allow you to use the lumen and beam angle specifications that is published on the manufacturer of the fixture as a means of guiding you in your lighting needs. You should of checked the lumen count too.