One of the most important principles to understand when designing a recessed lighting design is the angle of the beam. In recessed cans, the light is produced in the shape of a cone. You imagine the light starting as a point on the lamp and forming a circle on the ground. The beam angle is the angle of this light away from the bulb. For example, a 60 degree beam angle will produce a circle of light approximately 9 feet wide on the floor if the fixture is 8 feet from the floor. See a
Diagram.
That is only part of the formula. That circle of light that we now have on the ground is not all of the same intensity. About five and a half feet of that circle is a good bright light, while the rest spills out and diminishes as you get further from the center. This is very important to understand. With this information, you can overlay the light spill so that you end up with a nice even light pattern across the entire area you’re trying to light. One thing to remember when planning this is something called a work plane. This is an area approximately 30″ above the floor. This is an area where most tasks take place.
The work plane is important because as the distance between the luminaire and the surface to be illuminated decreases, the circle we were talking about also decreases. In a living room or family room, it is fine to design the lighting plan so that we have even light on the floor. However, in a kitchen, this work plane becomes much more critical. This is why in a kitchen, keeping recessed lights about 4 feet apart creates a pattern that is level on the work plane with the bright part of the circle.
There are a few other things besides the bulb and the can that shape the light pattern. The finish of recessed lights may vary the light pattern. A wallwasher creates a half cone that can be directed at a wall or fireplace. A fixed point bead can direct light in a very narrow beam to illuminate a small object.
This should give you a basic idea of what is involved when doing recessed lighting design. If you would like more information or have questions, please visit us at the links below.
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