Facts About Light
- Visible light is that part of the electro-magnetic spectrum that lies between the wavelengths of ultraviolet and infrared.
- White light is all colours: a rainbow is white light split up into its component colours.
- Sunlight contains, more or less, equal portions of all colours of visible light, ultraviolet (UV) and infrared.
- Northern sunlight (i.e. in areas north of the fortieth parallel) has more blue and UV than equatorial sunlight because of the greater absorption of all other colours, or wavelengths of light, by the atmosphere.
Forms of Artificial Lighting
Incandescent (or Tungsten) Lighting
These were the universal screw-in or bayonet bulbs in most homes consisting of an incandescent bulb with a tungsten filament in a near vacuum. Incandescent light is biased heavily toward the red spectra.
Advantages: Low cost for initial purchase.
Disadvantages: Inefficiency, low output of light for energy level.
Effect on light sensitive patients: Generally safe although very light sensitive individuals may need to avoid high wattage bulbs.
Halogen Bulbs
A variation of the incandescent bulb, it involves a more complex process whereby UV generated by the inner capsule is filtered by the outer capsule. Halogen lamps are 25-30% brighter than regular incandescent bulbs and remain brighter, longer.
Advantages: Efficiency. They last about twice as long as regular incandescent bulbs and give off 95% of their initial light output at the end of their lives.
Disadvantages: They are on average 5 to 10 times as expensive as their non-halogen counterparts.
Effects on light sensitive patients: Many report a severe adverse reaction to halogen bulbs, as they emit more UV and blue light than their Tungsten counterparts.
Fluorescent Lighting
They emit about four times as much light per unit of electricity as incandescent lights but are more complicated to install. The mechanism of fluorescent lighting involves the emission of UV and E-field radiation. Fluorescent tubes come in hundreds of shapes, sizes and spectral output.
Advantages: Cheaper to run.
Disadvantages: More expensive to install.
Effects on light sensitive patients: Because fluorescent lighting involves the emission of UV radiation it is unsafe for light sensitive individuals (unless covered by protective film or of the 'double envelope' type) and for many, unless the ballast is at least 5m from the sufferer. Research by German scientists at Berlin's Alab Laboratory indicates that compact fluorescent lamps released several cancer-causing chemicals (April 2011).
HID (High Intensity Discharge) Lamps
These are the big bright lamps you see in grocery stores, street lighting and industrial lighting. These lamps produce a lot of light quite efficiently.
- There are three types of HID lamps:
- Mercury Vapour: has a decided bluish cast (particularly unsafe for light sensitive patients).
- Metal Halide: contains all the spectra (so not suitable for light sensitive patients).
- Sodium Vapour: emits monochromatic (pure) yellow light.
Advantages: Sodium Vapour lamps are ten times more efficient than incandescent bulbs, in fact these are the most efficient bulbs made and one of the cheapest HID bulbs to purchase.
Disadvantages: Yellow tone of light.
Effect on light sensitive patients: This spectral range has no adverse effect and can safely be used for floodlighting and lighting of public places.
LEDs (Light Emitting Diodes)
Heralded as the lighting of the future, it is predicted to be the standard form of lighting in 10 to 15 years because it is the most efficient form of lighting to date.
Advantages: Very economical, with the most long-lasting bulbs.
Effects on light sensitive patients: At present most LEDs emit too much blue light. The more sophisticated LEDs are available according to exact colour specifications, measuring wavelength nanometres - blue, green, yellow, red - or a combination giving white light. Unfortunately we have not had any reports of light sensitive patients tolerating LEDs of any kind and many have developed severe headaches following exposure. A study (Environmental Science and Technology, January 2011) has found that LEDs contain lead, arsenic and a dozen other potentially hazardous substances.
Planning for the Future
Possible New Lighting Solution
We have received information of a new lighting solution from Vul Corporation, a developer and manufacturer of mercury-free, energy-efficient, general illumination lighting technology. Vul have created a bulb - R30 Electron Stimulated Luminescence (TM) - which is a direct replacement for the 65w incandescent flood bulb. ESL (TM) technology provides the same light quality as an incandescent bulb and fits neatly into classic light bulb shapes familiar to consumers everywhere. We are very interested to discover whether this energy - efficient, environmentally friendly and cost-effective lighting solution can effectively replace the traditional incandescent bulb, although only trials involving light sensitive patients can confirm the safety of this product for our members.
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