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suit their particular preference, and as most of them chose luminance _ needed for the lowest possible cost and where quality is deemed of lit- levels consistent with current recommendations or lower, Veitch and tle or no importance, e.g., for factories, warehouses, power plants, Newsham recommend lighting solutions that are as flexible as possi- mines, streets and highways, tunnels, garages, etc.—as if such places ble, with dimmable lights, local switching and wiring that allows one _ aren't usually unpleasant enough without the light adding to it! Even to move things around.’*'* though better-quality lamps have been introduced during the last Giving each individual as much control over lighting conditions as_—_ decade or so, these are mostly used indoors in commercial locations possible sounds like a very good idea, since lighting requirements may _and situations. vary considerably depending on a person's age and the type of activity. The most common types of HID lamps are: Too much light at the wrong time or in the wrong place can be just as * Mercury lamps. These are high-pressure lamps (as opposed to irritating and uncomfortable as too little. Also, it seems there are big ordinary FL tubes which are low-pressure mercury lamps) and pro- differences as to individual preferences. Even though more than half duce a spooky blue-white light of poor quality and relatively low effi- of those asked by Veitch and Newsham liked to work ina uniformly cacy compared with other HID lamps. Why they are still used as bright room, 17% preferred to have most of the light on the desk and _ streetlights is a mystery. In my opinion, they really ruin the nice the rest of the room more dimly lit and 7.5% liked an even darker —_ atmosphere of old cities and villages, and certainly don't do anything room." for the more modern ones, either. One study by Kellner et al. (1997) also found that agoraphobic * Metal halide lamps. These are about twice as effective as the patients felt most comfortable with luminance levels that were much — mercury lamps and contain other metallic elements besides the lower than those preferred by healthy controls.'* Another study by —_ mercury that give them a bright white or silver-white light with Veitch and Newsham (1998) showed women to be somewhat more moderate to "accurate" colour rendering. The best ones are often used sensitive to bright light than men were.'* in shops, convention halls and stadiums. They are also used in film I would of course also like to see incandescent light included as an _and TV studios, replacing the previously used tungsten halogen lamps option, especially since so many seem to dislike FL. Unlike what that were always appreciated for the way they made colours come many seem to think, it wouldn't have to cost very much more tohave _ alive but unfortunately also produced a lot of heat. incandescent instead of fluorescent * Low-pressure sodium (LPS) lamps. light at work, if you used the most These are very bright orange, budget effective halogen spotlights and flood- lights with zero colour rendering, since lights and used only as much light as they only reproduce a single wave- needed where and when ts reeded Another study by Veitch and rength. ae used fo bes and in many ubes are equally bright all day places still are, used to illuminate tun- and everywhere, and are not quite as Newsham (1 998) showed nels, highways, etc. If prolonged expo- e ficient as is usually claimed. First of women to be somewhat more sure to monochromatic light of warm all, if they are powered by convention- ay: . : colour has the same effects on humans al ballasts, those ballasts use about sensitive to bright light as on animals,” this is the light we 20% of the original installed effect. than men were. should avoid staying in for too long and Secondly, most tubes as they age lose much of their output (which is then turned into heat), especially if not cleaned regularly. After three years in these LPS lamps are that they give up to arelatively clean environment, the loss four times more light per watt than the of light may be as much as 50%, even though the tubes still use the mercury lamps, that colour rendering doesn't matter outdoors (I don't same amount of electricity. Plastic diffusers also steal some of the understand why it shouldn't), and that the eye cannot distinguish light and tend to make it too hot for the tubes to function optimally. _ colours at low lighting levels. I disagree particularly with that last The same goes for fixtures with four tubes.” statement, since those levels at which the eye can no longer distin- So let's say you have a standard class III tube that is said to give 50 — guish colours are so much lower than those created by LPS lights. lumens/watt. This sounds like a lot more than an incandescent bulb _ Perhaps there may be a biological reason for these differences in opin- that gives about 14 lumens/watt, or a halogen that may give something _ ion, since female eyes are usually better at distinguishing colours, like 22 Im/w, doesn't it? But then take away 20% right from the start, | whereas men instead have more rods in their eyes and see better in a bit more if you have a plastic diffuser, and then another 10-15% near darkness.” every year, and the difference is significantly smaller. My experience when driving on highways lit by LPS lamps is that For those who might still prefer FL, warm-white HF-powered slim _ the light is tiring on the eyes because it's so unnatural to see only a sin- class-II tubes, which give up to 100 lm/w in the beginning anddo not _ gle colour for a lengthy time. There are safety implications, too, as lose so much light as they age, may both save a lot of energy"* and _you really don't see things as clearly in coloured light as in a white or stop subjecting the nearby wildlife to in rural areas. The most common excuses for using improve the quality of the light to a level that can at least be accept- warm-white light with good colour rendering capacity. able to work in if you're not too sensitive or choosy, especially when + High-pressure sodium (HPS) lamps. Standard HPS lamps have used in modern two-tube luminaires with deep parabolic reflectors. about the same output as metal halide lamps and produce a bright Warm-white metal halide lamps in recessed downlight fixtures is peach-coloured light of poor to moderate quality that I find acceptable another energy-efficient and fairly attractive alternative. along highways but which looks unnatural in cities, villages and suburbs. There are now HF-powered HPS lamps with improved Industrial and Outdoor Lighting colour rendering that produce a more attractive and fairly Ever since FL and high-intensity discharge (HID) lamps were incandescent-like light, but since they are slightly less effective than forced on the public on a massive scale in the 1950s and 1960s, there other HPS lamps and require specially designed luminaires, they are has been this "tradition" in lighting guidelines to recommend FLor _ usually reserved for lighting picturesque tourist areas at night and HID lights of low quality for places where as much light as possible is places where the more affluent and influential work or reside. Another study by Veitch and Newsham (1998) showed Industrial and Outdoor Lighting Ever since FL and high-intensity discharge (HID) lamps were forced on the public on a massive scale in the 1950s and 1960s, there has been this "tradition" in lighting guidelines to recommend FL or HID lights of low quality for places where as much light as possible is 44 = NEXUS JUNE — JULY 2003 women to be somewhat more sensitive to bright light than men were. www.nexusmagazine.com