LED FAQ
How to evaluate the light output of an LED lighting system?
Until recently, the lighting industry and users alike have used “watts” to measure the luminous intensity of a light bulb. Since the arrival of LEDs, the industry has turned to the “lumen” as an accurate unit measure of the luminous intensity of the light source. The reason for this is very simple; the intensity of LED products tends to vary considerably from one manufacturer to the next. It is possible that a 10W LED bulb from one manufacturer will produce twice the amount of light as that of its competitor. The lumen unit measure describes the quantity of light perceived by a human being, therefore it is more appropriate to address this type of possible variation in wattage vs. perceived intensity. The performance of a LED bulb is largely dependent on the brand and model of the LED chipset used, the color outputted as well as the quality of the raw materials used to build it. Therefore, it is important that while shopping for LED products that you also look at the efficiency of the bulb, which is measured in lumens per watt. These helps sort through the immense variation in the quality of LED products offered in today’s market.
How to choose the appropriate lighting color?
Most lighting used to be sold only in one color, warm white, which we saw in typical incandescent bulbs and halogens. The exception was fluorescents, which came in a cool white. Nowadays, with LED technology it is possible to choose from a large range of whites and other colors. LED technology permits a level of unsurpassed customization depending on the application, something that was not available ever before to this degree.
Measured in Kelvin (K, SI Unit of absolute temperature), colors can vary from “warm” and cozy to “cool”, crisp and clean, depending on the effect you’re looking for. Here are the different white color offerings available today:
Warm White (2700-3000 Kelvin)
This color is as close to a typical incandescent light bulb or halogen. We suggest this color for common areas where …
Natural White (4000-4500 Kelvin)
This color of white is still close to your old incandescent bulb,but has a bit of refreshing white to it.
Neutral White (5000-5500 Kelvin)
Neutral white is also referred to as “daylight”. Expect a nice crisp white that helps define other colors it shines on.
Cool White (6000-6500 Kelvin)
This color is considered a colder bluish white. It’s ideal to light valuable objects in a display case of a storefront, but also expo halls and often found illuminating the building facades.
What level of output (lumens) do I need?
This may seem easy to figure out at first glance; however, it isn’t that simple when you consider all the technicalities of lighting a specific object, room or building. Generally, we suggest using the following empirical rule to determine the output required to light a room: multiply the area of the room (length by width in feet) by the coefficient of 22, which gives you the number of lumens you require to correctly light the specified space. Example: Take a room that measures 12ft x 16ft (12 x 16 = 192 sqft). Then multiply 192 x 22 = 4224 lumens. This means you need a lighting solution to the equivalent of 4 LEDs of 10W, each producing 1050 lumens.
It is recommended to distribute light starting with a minimum of 3 sources or lighting fixtures. Then, instead of using a single light in the middle of the room to produce most of the lighting, we propose you use a variety of sources such as lamps, suspended light fixtures, wall fixtures and table lamps. This will allow you to adapt the room’s lighting in function of your needs.
IIt’s important to understand that the empirical rule that we just described remains an approximation and that to further optimize the lighting of a room, we must consider the type of room we’re lighting. For example, we know for a fact that a kitchen, due to its purpose requires more light than a bedroom. Therefore, the number of lumens required for a room will depend largely on its dedicated use.
Here are a few examples of required lighting output according to the IESNA (Illuminating Engineering Society of North America):
Flooring : 20 lumens per foot
Tables and elevated surfaces : 30 lumens per square foot
Desks and other work tables : 50 lumens per square foot
If we take the 12x16ft example from earlier, saying it is a kitchen, we would measure the surface by number of lumens per square foot: 12x16x50 =9600. This room would then require 9600 lumens. However, if our room is a single color, we would use the x20 multiplier and therefore only 3840 lumens would be required.
Choosing the best projection angle for your lighting project…
For directional lighting installed in the ceiling, such as recessed or track lighting used to accentuate decorative objects, paintings or signage, it is fundamental to take into account the size of the object and the distance from the light source. The further the object, the slimmer the angle of projection will be in order to provide focus on the object and not light anything else. On the other hand, the closer the object, the projection angle of the light source will be much wider. Below you will find the typical projection angles used in function of the ceiling height given. We will use a projection angle of 60 degrees for a ceiling that’s 2.5-3.5 meters high, an angle of 38-40 degrees for a 3.5-4.5 meters high and an angle of 24-30 degrees for a ceiling taller than 5 meters.
When you light a space such as a stairwell allowing you to pass from one floor to the next, the projection angle must increase to 60 – 90 degrees and the output must be increased in order to ensure safety.
Remember that as you reduce the projection angle, you increase the output intensity of the light on what should be a smaller surface.
