Understanding LED Light Bulbs
Q: It used to be easy to replace a light bulb; now there are so many options, I don’t know what to choose. What do you recommend?
A: It’s hard to imagine a household commodity that has changed more in the last five years than the light bulb. The incandescent bulbs we all grew up with wasted a lot of energy and have been phased out. Government mandates ushered in the brief reign of the more efficient, but widely despised, compact fluorescent bulbs, or CFLs, which emit terrible-quality light and are difficult to dispose of because of their mercury content. The public’s loathing of CFLs accelerated the development of light-emitting-diode bulbs known as LEDs, which now rule the lighting world. These use up to 80 percent less energy than the old incandescents and can last for decades. LEDs are improving all the time and their prices are coming down. However, the quality of light they produce varies significantly, so it’s helpful to understand some lighting nomenclature before you buy.
Most LED bulb boxes have a Lighting Facts label that indicates brightness (measured in lumens), color temperature (labeled K for Kelvin temperature), energy use, estimated energy costs, and expected life. Since most packages also specify the type of incandescent bulb the LED replaces, you don’t need to pay much attention to the brightness measure. Instead, zero in on color temperature: 3,000K is my recommendation for a universally flattering, warm-white light. Anything higher is going to have a cooler, bluish-white cast. Another good measure is the Color Rendering Index, or CRI, which tells you how accurately the bulb renders colors compared to an incandescent bulb, which has a CRI of 100. For LEDs, a CRI of 80 or higher is best.
To ensure an LED will fit in your fixture, bring your old bulb with you to the store and compare the bases. The splayed fins that LEDs have to dissipate heat make them larger than other bulbs. Make sure the bulb is dimmable (you may need to replace your dimmer switches with LED-friendly ones to avoid annoying flickering or buzzing). And if you plan to use the bulb outdoors and/or in an enclosed fixture (some LEDs require more airflow than these lights provide), check that these applications are noted on the box.
If you haven’t already, now’s the time to embrace this new technology — unlike previous innovations, this one is here to stay.
What is Light?
Light is part of the electromagnetic spectrum of energy. It is a form of energy that we can see. Light is created when an energy source emits energy in the visual spectrum which is between 380 and 780 nanometers.
|Incandescence at its Best!|
Light is created in a number of ways. Incandescence is the most common way. Incandescence is burning. In an incandescent light bulb the filament is heated until it glows. This is true in the common A lamp as well as halogen and xenon light bulbs. Arc discharge is another way light is created as in fluorescent or High Intensity Discharge lamps. Arc discharge occurs when an electrical current is passed through a gas. Another relatively new way to create light is Solid State Lighting, better know as LED. Light is produced when electrical current passes through a semiconductor and light is emitted as a photon.
Perhaps the best example of incandescence is the sun. The sun is an example of natural light. Daylight is sunlight reflected and diffused through the atmosphere. Moonlight is sunlight reflected. There is no single type of natural light. There are even some plants that give off light directly. They are luminescent.
It is important to know about light, light sources and qualities of light in order to more effectively design lighting for a home. Remember, from a previous post, the color you see is in the light source. If the light source does not have a full spectrum of colors, you will not see the colors that are missing from that light source. That is why early fluorescent and LED light sources did not render colors accurately; they were missing colors in the spectrum.
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