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4 LD+A/April 1999 HID (high intensity discharge) may not be the best option for many lighting applications for two reasons: (1) many recent improvements in fluorescent lighting, and (2) a more accurate way of measuring how the human eye really perceives light. In our LIGHTFAIR seminar, “Fluorescent vs. HID: 10 Rounds in the ESSAY BY INVITATION Stan Walerczyk Brooks Sheifer High Bay Arena,” * we discuss how both fluorescent and HID have evolved. Attendees will learn how HID competes with T8, T5, Tri-loop, and induction fluorescents. We evaluate fluorescent and HID characteristics including warm-up and restrike times, dimming, photometrics, CRI, S/P ratios, lumen depreciation, luminaire appearance, cost, and maintenance. Improvements In Fluorescents This decade has produced dramatic improvements in fluorescent lamp and electronic ballast technology. The existing CRI (color rendering index), light output, and efficiency packages are quite awesome. There are basically five systems: 1. The 85 CRI (daylight has a 100 color rendition index) 4 ft F32T8 lamps with high power 1.15–1.20 BF (ballast factor) electronic ballasts. 2. 40–55 W bi-axial lamps with electronic ballasts. 3. Three-loop compact fluorescents with electronic ballasts. 4. Straight T5 lamps with electronic ballasting (although the lm/W is no better than T8s with electronic ballasts, the T5 system provides more lumens per lamp foot and better control of the light because the lamp diameter is smaller). 5. Induction fluorescents without electrodes, which have a 100,000 hour rating at 64 percent of initial light levels. * “Fluorescent vs. HID: 10 Rounds in the High Bay Arena” will be presented at LIGHT- FAIR on Thursday May 13, 2:00–3:30 p.m. All of these fluorescent systems have high brightness and intensity, not just sufficient lumens. This is why at a distance, a single 100 W incandescent lamp is seen much easier than two side-by-side 60 W incandescent lamps, even though both conditions have the same lumens. Another example is an old drum fixture with thick white glass lens and 75 W incandescent lamp that we tried to retrofit a few years ago. First, we replaced the incandescent lamp with two 13 W compact fluorescents. That did not provide enough light. Then we installed a third 13 W compact fluorescent. That still did not make much difference. We could have filled the fixture with 13 W fluorescents with little gain. Although the lumens from the three 13 W compact fluorescents more than doubled the lumens from the one 75 W incandescent lamp, the fluorescents were not bright or intense enough for the light to get through the thick white lens. So we ended up replacing the entire fixture. The new fluorescents are able to deliver long range punch and penetrate translucent material. These fluorescent systems also feature instant-on with no restrike time, so they can easily be used with frequent on and off switching, photocontrols, and occupancy sensors. Fixtures with more than one ballast can have multilevel lighting. Dimming ballasts can also be used with fluorescents, and there is a fairly linear relationship between light level and wattage. HID fixtures often burn for extended periods only because of their unacceptable warm up times and restrike times. This wastes a ton of electricity. Fluorescents are a linear, or area, light source, so there is less shadowing, contrast, and glare. When used with electronic ballasts, there is no stroboscopic effect. Many maintenance people prefer fluorescent systems because if one or more of the lamps or ballasts burn out in a fixture those remaining keep operating normally. With HID fixtures, if the single lamp or ballast burns out, there is a large dark area that needs attention as soon as possible. One plus for HID is if the maintenance staff uses a pole with bulb changer, then HID maintenance Publisher William Hanley, CAE Editor Mark A. Newman Assistant Editor Roslyn Lowe Associate Editor Kevin Brady Art Director Anthony S. Picco Associate Art Director Angel M. Roque Columnists Christopher Cuttle Louis Erhardt John Kesselring Michael Lane Bill Thornton Book Review Editor Paulette Hebert, Ph.D. Director of Marketing Beth Bay Advertising Coordinator Celeste Picco LD+A is a magazine for professionals involved in the art, science, study, manufacture, teaching, and implementation of lighting. LD+A is designed to enhance and improve the practice of lighting. Every issue of LD+A includes feature articles on design projects, technical articles on the science of illumination, new product developments, industry trends, news of the Illuminating Engineering Society of North America, and vital information about the illuminating profession. Statements and opinions expressed in articles and editorials in LD+A are the expressions of contributors and do not necessarily represent the policies or opinions of the Illuminating Engineering Society of North America. Advertisements appearing in this publication are the sole responsibility of the advertiser. LD+A (ISSN 0360-6325) is published monthly in the United States of America by the Illuminating Engineering Society of North America, 120 Wall Street, 17th Floor, New York, NY 10005, (212) 248-5000. Copyright 1998 by the Illuminating Engineering Society of North America. Periodicals postage paid at New York, NY 10005 and additional mailing offices. Nonmember subscriptions $39.00 per year. Additional $15.00 postage for subscriptions outside the United States. Member subscriptions $30.00 (not deductable from annual dues). Additional subscriptions $39.00. Single copies $4.00, except Lighting Equipment & Accessories Directory and Progress Report issues $10.00. Authorization to reproduce articles for internal or personal use by specific clients is granted by IESNA to libraries and other users registered with the Copyright Clearance Center (CCC) Transactional Reporting Service, provided a fee of $2.00 per copy is paid directly to CCC, 21 Congress Street, Salem, MA 01970. IES fee code: 0360-6325/86 $2.00. This consent does not extend to other kinds of copying for purposes such as general distribution, advertising or promotion, creating new collective works, or resale. POSTMASTER: Send address changes to LD+A, 120 Wall Street, 17th Floor, New York, NY 10005. Subscribers: For continuous service please notify LD+A of address changes at least 6 weeks in advance. This publication is indexed regularly by Engineering Index, Inc. and Applied Science & Technology Index. LD+A is available on microfilm from University Microfilm, Ann Arbor, MI.
is easier. Replacement lamp costs are about the same. For example, eight F32T8 lamps cost about the same as one 400 W HPS or metal halide lamp. HID technology has not stood still. The most significant ongoing improvement is pulse start metal halide lamps and ballasts with ignitors to drive them. This system provides substantial gains in lm/W, lumen maintenance, color stability, shorter warm up times, shorter restrike times, and minimum ambient temperature starting. Lamp life can also be extended. This system could replace standard metal halide and HPS. Currently there is a price premium, but much of that could evaporate down the road. There are other HID improvements, such as energy saving lamps, extended life lamps, double arc tube lamps, high CRI, electronic ballasts, two stage (highlow) systems with occupancy sensors and/or photocontrols, and fixtures with quartz backup, but most of these upgrades are quite expensive. Some have drawbacks. An example is color corrected HPS lamps that have much better color rendering, but also higher cost, reduced light output, and shorter lamp life. Electronic HID ballasts consume less wattage than magnetic HID ballasts, but HID lamps draw the same wattage either way. Although the two stage systems for HID do reduce power at low stage, it is not linear. At 50 percent light output, wattage is considerably higher than 50 percent often in the 60–70 percent range. Better Way To Measure Light The long established way of measuring the amount of light a source produces has been the photopic lumen. The lumens listed in lamp catalogs are photopic lumens. It is very easy to perceive that photopic lumens are not realistic. Following are two examples. Compare 14,000 photopic lumens 175 W, 65 CRI standard metal halide with 16,000 photopic lumens 150 W, 22 CRI standard HPS. Metal halide and HPS are the two most common types of HID. Although the metal halide has slightly less photopic lumens, virtually everyone perceives that it is brighter than the higher photopic output HPS. Another example is four various color tone fluorescent lamps with not only almost identical photopic lumens but also identical CRI. When an F32T8 830, F32T8 835, F32T8 841, and F32T8 850 lamp are compared, almost everyone perceives the 850 lamp the brightest, followed by the 841 lamp, the 835, and the 830 lamp the least bright. With the substantial inconsistency between photopic lumens and general perception, we no longer base lighting recommendations on just photopic lumens or light meter measurements. Things got more scientific after we stumbled on Sam Berman’s work on pupil lumens (later called task modified lumens) all beautifully explained in his and Brian Liebel’s “Essay By Invitation” in the November 1996 LD+A. 1 Photopic lumens are based on the eye’s two degree central field of vision. This is only 0.02 percent of the human total visual field. There are two types of photoreceptors: cones and rods. In this two degree central field of vision, cones are the main photoreceptors and photopic lumens are based on cone sensitivity. Rods, which greatly outnumber cones, are excluded in photopic lumens. The peak sensitivity for rods is in the bluegreen region of the spectrum, compared to green-yellow for cones. Scopotic lumens are based on rod sensitivity. Both cones and rods contribute to how the eye perceives light for daytime tasks. S/P (scotopic/photopic ratios) can be used as a tool to show how the human eye really sees. Page 79 of the 1996 Philips Lighting’s Lamp Specification and Application Guide has S/P ratios for many fluorescent lamps, including 1.83 S/P for F32T8 850 and 1.62 S/P for F32T8 841. In addition to that listing, standard 40K clear metal halide has 1.49 S/P, standard HPS has 0.62 S/P, and low pressure sodium has 0.40 S/P. For the vast majority of applications the higher the ratio the better. Berman and Liebel listed three task application factors for various tasks. For general evaluation we tend to use the 0.78 exponent, where good vision is a requirement. photopic lumens x (S/P) 0.78 = initial task modified lumens We believe that worst case, when lamps are old, is more relevant, so we include lumen maintenance in the equation. photopic lumens x (S/P) 0.78 x lumen maintenance = end-of-life task modified lumens Generic composites of a variety of lamp and ballast combinations are shown in Table 1. Recent Applications Contra Costa Newspapers, Walnut Creek, CA Circle 13 on Reader Service Card.
Page 2 and 3: CONTENTS LIGHTING DESIGN INTERNATIO
Page 6 and 7: Table 1— Generic composites of va
Page 8 and 9: 210 to 101. Photocells were also in
Page 10 and 11: Color Dr. Richard Corth explains,
Page 12 and 13: P H O T O N S NOTES ON LIGHTING DES
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Page 16 and 17: Power Ads The advertising dynamos a
Page 18 and 19: San Francisco Shines at LIGHTFAIR S
Page 20 and 21: LIGHTFAIR Events continued from pre
Page 22 and 23: 1998 INTERNATIONAL ILLUMINATION DES
Page 24 and 25: TUNNEL VISION Located in west Paris
Page 26 and 27: The worlds of art and architecture
Page 28 and 29: The Guggenheim Museum Bilbao is the
Page 30 and 31: (below) By highlighting the water,
Page 32 and 33: LIGHTFAIR INTERNATIONAL SEMINAR PRE
Page 42 and 43: LIGHTFAIR INTERNATIONAL LIGHT CHAT
Page 44 and 45: was more than happy to oblige and h
Page 46 and 47: Opportunities abound for manufactur
Page 48 and 49: most plush and dramatically lit dan
Page 50 and 51: efficient source for display downli

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