Words By Roy Furchgott, The Washington Post
Technology transforms lighting design at lightning speed, yet there is still no better way to upgrade to your home lighting than choosing the right light bulb. To get started you need to understand the most critical measurements: lumens, kelvin and the colour-rendering index.
The first question to ask yourself, according to Terry McGowan, director of engineering for the American Lighting Association, is: How much light do you need? To get an answer, he said, “unfortunately means learning what a lumen is.”
A lumen measures quantity of light – how bright it is. “More lumens translate to more light,” said Shaun Fillion, who runs the master’s in lighting design program at the New York School of Design.
Many people are used to choosing brightness based on watts. Watts measure how much electricity a bulb uses “but no longer indicates how bright a lamp might be,” Fillion said. The lumen measurement is more precise. “If you have a lightbulb you want to match, look to match the lumens,” McGowan said.
The next important measure is correlated colour temperature. “Temperature is measured in kelvin,” McGowan said. “It’s an odd scale, but blame it on the kelvin people.” This scale tells you how amber or blue a light appears to be, and does so precisely, unlike the designations like soft-white or daylight.
There is no best colour, it’s a matter of personal preference. But experts suggest that you pick a colour and stick with it. “I’ve been in rooms with mixed warm and cool bulbs, and pretty soon your head wants to explode,” McGowan said.
Colour rendering index
The most overlooked measure, but in some ways the most critical, is the colour-rendering index. That tells you how accurate colours look under the light. “The colour rendering index is more important for me than lumen output,” said Rosemarie L. Allaire, a California-based residential lighting designer. Good colour rendering light lets you tell whether a sweater is navy or black.
The CRI, as it’s called in the industry, is a scale from 0 to 100. “Daylight is 100. You can’t render it better than that,” Allaire said. “When I am looking for an LED replacement for myself or a client, the first thing I look for is colour rendering, and if it’s not 90 or above, I don’t buy it.”
A light can be a warm amber and still score high on the CRI scale. “Even in yellow, high CRI Light, blue artwork should look blue,” Fillion said.
There is still the matter of dimming, which gets complicated if you are using anything other than old-fashioned incandescent lights.
Whether your wall dimmer will work with a given bulb – even one that says it is dimmable – still depends on the kind of dimmer you have. To make it even more confusing, some bulbs can be dimmed by more than one kind of dimming switch, but not necessarily all dimmer switches. You can check the specifications, but even that is no guarantee. The best choice is to take a bulb home and try it.
But some LEDs offer another way to dim, using smart technology and a wireless connection like WiFi, Bluetooth or ZigBee, and can be controlled by Alexa, Siri or Google Home. This technology puts the dimming technology in the bulb itself, rather than in the electrical switch.
These LEDs also offer other features that you won’t find in common bulbs, like the ability to change colours, to turn on at specific times, and to control the colour and brightness they will be during different times of day.
Featured Image: Natalia Y, Unsplash