After finally getting stuck into some building I returned to my lighting research with renewed energy. Inspired to tackle my work with a slightly more hands-on approach I pulled out a couple of light bulbs from our hallway cupboard to have a look for myself. Funnily enough, the cardboard boxes proved the more interesting and soon I was reading the information the manufacturers consider major selling points.
What is a watt?
Watts measure the energy consumed by a bulb.
During the dominance of incandescent’s, watts would be advertised as the measurement of brightness, yet when new lighting technologies were introduced this could no longer be a sound gauge for consumers. This is because halogens and LEDs use less wattage to create the same amount of brightness. For example; a 100-watt incandescent bulb provides 1600 lumens, whilst you only need a 22 watt LED to achieve the same result. If you used a 100 watt LED, you would be looking at an outdoor floodlight!
Flipping the box over I found a table detailing the specifications of the globe- voltage, frequency, colour, and output. I break down each one below:
Voltage measures the pressure of an electric current.
It is suggested to think of voltage through the terms of water tanks. The water stored in the tank is the charge. The pressure of a connected hose represents voltage. The more water in the tank (battery), the higher the pressure (voltage). As the tank is drained the pressure decreases, just like a torch dims as the batteries run low.
Mathematically, a volt is the amount of joules per coulomb.
Or in English, the amount of work per group of flowing electrons.
In the case of my lightbulb, the voltage is 240V. As mentioned here, electricity enters your home at 240 volts. When the lightbulb is connected to the home’s circuit (240v) it should deliver the advertised lumens. If you connect this bulb to a lower voltage it will continue to work but will be dimmer than advertised. If you use a bulb recommended for a lower voltage, the light produced will be brighter, but the globe will have a shorter lifespan.
What is frequency?
This is the invisible flickering of a light bulb connected to AC- it is the pulse of the electricity pumping through the bulb. A frequency of 50/60 cannot be detected by the naked eye. However, if a frequency is too low the eye will detect the flickering which can cause headaches and eye strain. To be honest I don’t really understand the role frequency plays, but for now, that explanation will do.
What is colour temperature?
Colour temperature is exactly as it sounds, the colour of the light. It is measured in Kelvins. The higher the Kelvin (K) rating, the whiter the light will be. 1000- 3500k produces warm light, 3500- 4100k is neutral, 5000k up is considered cool. This scale remains the same for all lightbulbs.
- 1900k is candlelight
- 2000k or under will give a dim soft glow- good for ambient lighting.
- 2000 to 3000k is best for living rooms and bedrooms as they give a soft white glow.
- 3100 to 4500k for kitchens/workspaces, good for task lighting. (Bright bluish daylight too harsh for home ambient lighting.)
- 4800k direct sunlight.
- 6000k cloudy sky.
My lightbulb has a temperature of 2800k, meaning it produces a soft white light.
What are lumens?
Lumens is the measurement used to represent how bright a light is. It indicates the total light emitted, no matter the direction.
Lux is the unit used to measure the output of light in a given area, so 1 lux = 1 lumen metre squared. It is a measurement of the amount of visible light and intensity of the illumination. The centre of a lamp beam is where the light intensity is the highest.
Lumens and lux come into play when planning the lighting of your home when considering Ambient and Task lighting.
Ambient lighting should radiate a comfortable level of brightness and is considered the room’s ‘natural light.’ This is generally achieved through the use of omni-directional (light in all directions) lamps. Downlights will pool light on surfaces so should only be used for task lighting. They are not successful at achieving general illumination. Up to six downlights s would be needed to achieve the same result of an omni-directional light. Light shades can absorb almost half of your light so choose carefully.
Task lighting provides concentrated light for an area of work or reading. It has to be brighter than the ambient lighting to ensure contrast. Lamps and track lighting can be used if the direction needs to be changed. Under counter kitchen lights are used as fixed directional lighting. Task lighting needs to be free of glare and shadows, but bright enough to avoid eye strain.