d. LED Light Info

The LED lamp is a chemical light source, made out of tiny Light Emitting Diodes. 

Diodes have been used since the 1960s, as display- and indicator lamps in electrical devices and, more recently, as backlighting in flatscreen TV-, computer- and cell phone screens.

Using LEDs for general illumination is a newer invention, with some challenges as LEDs are by nature a) coloured; b) directional; c) very dim.

a) Adding a fluorescent yellow phosphor mix to blue diodes is the most common method for creating a (more or less) warm-white light in home lightbulbs.

Diagram from: www.gluehbirne.ist.org

b) The second challenge has been to make the light omnidirectional like incandescent light sources. Placing diodes around a central stick is one attempt to distribute the light in more directions.

c) The third challenge is to make LEDs high lumen while concentrated in a heat trapping bulb. The vast majority of all LED lamps for the home market are still low lumen, with only a few bright exceptions.

+ Most LED lamps light up instantly.

+ LEDs are said to have a long life (although with decreasing brightness).

• Only some LEDs are dimmable, so check the label.

- Light colour gets colder when dimmed (with a few exceptions not available for the home market).

- Light colour may also turn colder over time. 

Image from ScreenLight & Grip

- Lower colour accuracy (source: manufacturer catalogues) means that objects, people and food will look more grey and flat, and that rooms will look more dull and gloomy.

Lower colour rendition LED vs top quality incandescent downlights
(images from www.prweb.com) 

- Poor contrast, unclear light and sometimes flicker may cause eye strain and headaches.

- White LEDs have a higher portion of blue light which increases the blue light hazard (source: ANSES) and may be a risk to children's eyes and cause symtoms in light sensitive patient groups.

Spectral Power Distribution diagrams from: housecraft.ca

- Lower power factor (according to manufacturer catalogues) and can create dirty electricity.

LED Lamp Models

Note: 

These are examples of available models. LED lamps come in many different bulb shapes. Design details may differ between brands, and new models are constantly being introduced on the market. Not all models may be available in all countries or at all retailers. 

• Light colours range from "extra warm" (2100 K) to "daylight" (7000 K). 

• Being a developing technology, warm-white LEDs have the biggest quality variations between brands and lamp models when it comes to light colour, colour rendition, brightness and durability. 

• Label information is often not reliable: 

- Promised long life has yet to be tested in any consumer tests, so take those numbers with a grain of salt. LEDs are sensitive to overheating, which can affect actual life. And as they get progressively dimmer with age, expect to have to replace them sooner anyway. 

- Promised brightness may be less than the label says, e.g. an LED bulb marked "40W equivalent" may be more like a 25 or 30W equivalent, especially at the lower end of the market. Always check lumens and buy a slightly brighter lamp than you had intended to compensate for light loss and exaggerated label claims. 

- Promised light colour is only an approximate. An LED bulb marked "warm-white" may be anything from greenish-yellow or pinkish-yellow to blue-white, especially at the lower end of the market. Some of the best LED bulbs on the market are fairly bright and incandescent-like in light colour, though never exactly, and always with lower colour rendition. 

So, ask to see how it looks before buying if you want a certain light colour or brightness. And don't hesitate to take it back if it doesn't give as much light or look as good or as you expected in your home. Always save the receipt. 

 • LEDs are mercury-free but contain small amounts of other harmful elements (see Environment) so always leave burned-out LEDs for recycling. 

• Do not throw in the glass recycling bin!