In our last blog post, we talked about the “brightness” of landscape lamp illumination. We discussed the two measurements that determine an LED lamp’s perceived brightness, its wattage equivalent and its color temperature.
There is a third factor we have to consider in landscape lighting design, and that’s the “beam spread” of a light source. Simply put, the beam spread is how far the reflected light extends in all directions, or, how much space is actually illuminated by each lamp/fixture combination.
This is important because we use different lamp/fixture combinations to accomplish different effects in landscape and outdoor architectural lighting. Depending upon what specific feature we’re trying to highlight and what effect we’re trying to reach, landscape designs ultimately result in a ‘layered’ look which may include any combination of flood lights, path or area lights, uplights, down lights, and spotlights. When designed in consort, these combinations can enhance the curb appeal of the home, highlight architectural features, and/or increase safety and security of the property.
Beam spread refers to the measurement of how much a light source causes a light to spread. In other words, it can be used to determine how wide or narrow a beam of light is going to be. Different types of lamps offer various beam spreads. For example, it’s fairly simple to distinguish between floodlights and spotlights. In general, a spotlight will have a fairly narrow beam that’s less than 45 degrees wide, while a floodlight will have a beam that can spread up to 120 degrees or more.
To help visualize this, think about the lights in a parking lot. Because the objective is to provide light over a wide space, the light source will “flood” a large area. Placing the fixtures at an appropriate distance from each other allows the beams to nearly overlap, thus providing more or less continuous light that illuminates the desired space.
Conversely, think about an entertainment venue. When an individual on the stage needs to be singularly highlighted, a very distinct light “spot” will be used to illuminate the soloist and nothing else.
There is a calculation to determine the beam spread of a light source, and I’ll share with you the calculation provided by Illuminations USA, Inc. a landscape lighting company in the Orlando/Winter Park area of Florida:
“ . . . take the angle of the beam, multiply it by 0.018, and then further multiply that number by a distance. For instance, if a light has a beam angle of 50 degrees and you want to determine the spread at 20 feet from its source, you would multiply 50 by 0.018 by 20. This gives you a beam spread of 18, meaning the beam of light will be 18 feet wide when its 20 feet away from the source.”
And you thought landscape lighting was simple, didn’t you?
At Moonglow Lightscaping, we’ve learned which beam spreads are best suited to meet specific objectives.
For example, if we want to highlight specific elements like a column or an inset corner in the front of a residential home, we most likely will use what we consider a “standard” uplight. We will carefully place the fixture at the right distance from the wall so the light source highlights that area all the way “up” to the eaves of the home, but is fairly narrow so that it only illuminates what we need it to and doesn’t provide light anywhere we don’t want it to (like into a window).
Technically, that’s a spot light, because we're using lamps with a narrow beam angle of 38°. That lamp is placed inside an adjustable fixture which allows us to precisely set the light source where we need it to be to accomplish the desired effect. These “standard” lamps are usually 5 LED Watts (around 300 lumens, or a 30-35W incandescent replacement) with a color temperature rating of 2700. We use a lot of these.
We also often illuminate trees on a residential property. These lamp/fixture combinations may either be uplights or downlights, and they will have a wider beam, maybe 60°, so that the lighted area is wider.
If our customer is on a dark corner and is concerned about security, we may also provide a wider beam light down the side of the house, aimed toward the back of the home from the front. In this case, the fixture is placed so that the light source actually “washes” the wall by providing light all the way down the wall. Although the fixture is aimed mostly toward the wall, the light is actually reflected and will illuminate the area in front of the wall out to several feet. These are more like flood lights, but they aren't as bright as the parking lot example I used earlier. We actually call these “wash” lights. The beam on these can range from 60° to 110°.
Path lights are also very commonly used. The objective in that case is to illuminate a walkway or pathway or to provide an area specific light. In this case, the beam angle of the lamp itself isn’t as critical. The fixture is the deciding factor.
In a path light, the lamp sits under a “hat”, which is the circular cover at the top of the path light fixture column. The light shines up into the hat and then is reflected back down to illuminate the area beneath it. Depending upon the wattage of the lamp, the size and shape of the hat, and how tall the fixture is, the reflected light illuminates a circle of several feet in diameter for each fixture. By carefully placing these path lights to work with each other, we can completely illuminate a walkway or flower bed.
So, that’s a general view of “beam spread” in low-voltage landscape lighting. At Moonglow Lightscaping, we know what works best and we can advise you about what lamp to use where.
If you have any questions or would like more information about low-voltage landscape lighting, please contact us.