The Spectra of Choices in the Choice of Spectruma discussion about outdoor lightingand its consequences

David M. Keith, FIESIESNA SALC September 2004

Overview

l Sources– are what we use– & what we also get is: SPD, rated lumens, lamp life,

economics, energy use & ..mercury and associated pollution

l Radiation– is what we provide– & we also get: vision, color, safety/security & ..

health effects through melatonin regulation and of course light pollution - skyglow

Sources

l lamps convert electricity to radiation– which is perceived as light by human eyes– all radiation leaving a lamp has the same “profile”– the spectral power distribution (SPD) determines

many of the performance characteristics of the sourcel each source has a characteristic SPD

– continuous e.g. incandescent (& sunlight & daylight)– discrete aka “spikes” e.g. HPS– mixed - continuous with spikes e.g. MH & fluorescent

SPD: Sunlight (6500K) and D65

0

0.0002

0.0004

0.0006

0.0008

0.001

0.0012

0.0014

0.0016

0.0018

360 400 440 480 520 560 600 640 680 720 760

SPD: Incandescent (CIE A, 2856K)

0

0.0005

0.001

0.0015

0.002

0.0025

0.003

0.0035

360 400 440 480 520 560 600 640 680 720 760

SPD: High Pressure Sodium

0

0.001

0.002

0.003

0.004

0.005

0.006

0.007

0.008

0.009

0.01

360 400 440 480 520 560 600 640 680 720 760

SPD: Metal Halide

0

0.002

0.004

0.006

0.008

0.01

0.012

360 400 440 480 520 560 600 640 680 720 760

SPD: Fluorescent - 30003000K to 65006500K

0

0.002

0.004

0.006

0.008

0.01

0.012

0.014

0.016

0.018

360 400 440 480 520 560 600 640 680 720 760

Source choice has consequences

l in general each source has characteristics that make it attractive for some occasions:

Incandescent great color & dimmableHPS long life & high lumensMH good color & high lumens Fluorescent long life & choice of colorSun/Daylight great color & long life & ...

Source choice has consequences

l in general each source has characteristics that keep it from being perfect for every occasion:

Incandescent short lifeHPS poor colorMH short life, lower lumensFluorescent poor optical control, coldSun/Daylight only on 12 hrs each day

l the key is to consider ALL the consequences

Lamp life and rated lumens

l Life– based on “50% of sample has failed”

l Lumens– basic measure of “output” based on photopic lumens– at start of life, because output changes over life– estimate change by Lamp Lumen Depreciation Factor

l Mean Lumens vs End-of-Life Lumens– mean based on lumens at 40% of life– choose the value for the application & maintenance

Lamp lumen depreciation

30%

40%

50%

60%

70%

80%

90%

100%

0 4 8 12 16 20 24

Hours of Operation (1,000's)

% In

itial

Lum

ens Probe-Start MH

Pulse-Start MH

HPS

CFL-HW

T5HO

Lamp economics

l “effective life” sets maintenance frequency– burn-out, loss of lumens, loss of color, or scheduled– determines the maintenance cost - materials & labor

l different sources have different issues

Incandescent very frequent lamp replacementHPS cycling at end of lifeMH shorter life, lumen depreciationFluorescent limited size and optical control

HID economics (HPS and MH)

l comparing HID sources for over 10,000 lms– HPS typically has 24,000 hr life (24,000+)– MH has been improving, now 12,000 to 20,000

l depends on type & position - pulse start (vertical) is longerl LLD may be determining factor

l for maintenance, MH costs about 3 times HPS– reported by AZ Report 522

l used new MH technology compared to std HPS equipment

– consistent with research by D. Keith in JIES

HID economics - and fluorescent?

l comparing to HID sources for over 10,000 lms– fluorescent typically has 20-24,000 hr life– depends on type & position & temperature perhaps– loss of optical control may be significant

l for maintenance, estimate that fluorescent almost equal to HPS and about one-third to one-half of MH– similar LLD and slightly shorter life than HPS

HID energy use (HPS and MH)

l comparisons of roadway lighting systems (D. Keith, JIES Summer 2002) show that MH systems have higher energy use than HPS– depending on the roadway class & number of lanes– “best MH” systems use 1.5 to 1.8 times as much

energy as “best HPS” systemsl one consequence of energy use is pollution

– air, water, land pollution associated with power plant– pollution from fuel production

Mercury pollution from coal power

l US EPA reports 48 tons of mercury released annually - mostly from coal power plants

l for each of 290 million citizens, that’s 135 mg/year of mercury into the environment

l EPA *ingestion* limits for each person is 0.1 micrograms per day and per kilogram of body weight - for 75 kilo (165 lb) this is 2.7 mg/year

l power plants are introducing mercury into the environment at 50 X “allowable ingestion” rate

Mercury pollution from MH lamps

l NEMA reports 40 million MH lamps in US, sol if each lasts 8 years, andl MH lamps have 1 to 100 mg Hg in each one, sol for the US, with 290 million population,l per person, that’s 0.2 to 1.7 mg/yrl compare with the EPA’s “allowable ingestion” for

a 75 kilo (165 lb) person of 2.7 mg/yrl MH lamps ~ 0.1-0.6 X “allowable ingestion” rate

Mercury pollution from FL lamps

l NEMA reports 1,100 T12 & 800 T8 Megalamps l if on average a lamp lasts 8 years, andl T8 has 3.5 - 6 mg, T12 has 4.4 - 9 mg Hg, sol for the US, with 290 million population,l per person, that’s 3.4 to 6 mg/yrl compare with the EPA’s “allowable ingestion” for

a 75 kilo (165 lb) person of 2.7 mg/yrl FL lamps 1 - 2 X the “allowable ingestion” rate

Mercury pollution summary

l mercury is poisonous to humansl mercury migrates into the food chainl it accumulates and concentrates in seafoodsl the production of lamps and electricity introduce

mercury into the environmentl the rate of introduction is clearly greatest

through use of coal to produce electricity– most effective approach is energy efficiency

l fluorescent & MH lamps are hazardous waste

So what does this have to do with ...

l what about the radiation we are producing?– how much?– what color?– how are colors rendered?– how well can we see?

l and also– does it aggravate light pollution?– does it make us sick or ill?

l how does it work for people?

SPD: Incandescent (CIE A, 2856K)

0

0.0005

0.001

0.0015

0.002

0.0025

0.003

0.0035

360 400 440 480 520 560 600 640 680 720 760

SPD: High Pressure Sodium

0

0.001

0.002

0.003

0.004

0.005

0.006

0.007

0.008

0.009

0.01

360 400 440 480 520 560 600 640 680 720 760

SPD: Metal Halide

0

0.002

0.004

0.006

0.008

0.01

0.012

360 400 440 480 520 560 600 640 680 720 760

SPD: Fluorescent - 30003000K to 65006500K

0

0.002

0.004

0.006

0.008

0.01

0.012

0.014

0.016

0.018

360 400 440 480 520 560 600 640 680 720 760

Human visual sensitivity

l what is it? “our visual response to radiation”l foveal (2°), para-foveal (10°) or peripheral?l photopic, scotopic or mesopic?l transient adaptation factors?l aging effects like lens yellowing, adaptation?l “the standard” = foveal, photopic, young eyes

– used to measure all “lumen-ous” quantities– that may be a bad assumption for some tasks

l we still have a lot to learn about . . .

Sensitivity Function: PhotopicPhotopic

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

360 400 440 480 520 560 600 640 680 720 760wavelength (nm)

Sensitivity Function: Cones

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

360 400 440 480 520 560 600 640 680 720 760

wavelength (nm)

Color contrast

l color contrast includes both luminous (typical) and chromatic contrast - hue and tint matter!

l all evaluations based on lumens are spectrally ignorant - no color aspects considered at all

l research (Knox and Keith, IESNA Conf. 2003) indicates that using spectrally-informed calculation methods leads to significantly different reflectance and contrast results

l for “visibility” of red, orange and yellow info, HPS and incandescent may be better than MH

Color rendering

l photopic, foveal visual evaluation of sourcesl usually based on the CIE’s 13.3-1995 CRI -

Color Rendering Indexl the chromaticity difference DC describes the

tolerance for difference between the source being evaluated and the reference source

l tolerance limit for DC is 0.0054 MK-1

l if DC limit is exceeded, “.. resulting [CRIs] may be expected to become less accurate.”

CRI of sources with DC values

Source x y CCT CRI DC

Equal Energy 0.33 0.33 5455 95 0.0077 *C_D 0.31 0.33 6502 100 0.0000C_A 0.45 0.41 2856 100 0.0000HPS from 0.51 0.41 2001 16 0.0007

to 0.52 0.42 2174 21 0.0025MH from 0.37 0.39 3776 53 0.0067 *

to 0.40 0.40 4319 68 0.0101 *F30 0.44 0.41 2919 85 0.0013F35 0.42 0.40 3326 87 0.0002F41 0.39 0.38 3813 87 0.0004F65 0.32 0.34 6088 87 0.0025

Sensitivity Function: Para-foveal 10°

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

360 400 440 480 520 560 600 640 680 720 760wavelength (nm)

Sensitivity Function: Scotopic

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

360 400 440 480 520 560 600 640 680 720 760wavelength (nm)

Mesopic range & roadway criteria

the mesopic luminance range, with luminances associated with 7%, 18% and 50% reflective surfaces, for moonlight, as well as the very darkest roadway point and very brightest roadway point luminances, for meeting IESNA RP-8-00 criteria for roadway lighting0.001

0.01

0.1

1

10

Road 7% Area 18% MAX 50%

Lum

inan

ce (c

d/m

2) in

the

mes

opic

rang

e &

ro

adw

ay d

esig

n cr

iteria

Major_max

Local_min

Moon

Mesopic range & parking lot criteria

the mesopic luminance range, with luminances associated with 7%, 18% and 50% reflective surfaces, for moonlight, as well as the very darkest roadway point and very brightest roadway point luminances, for meeting IESNA RP-20-98 criteria for parking lot lighting0.001

0.01

0.1

1

10

Prkng 7% Area 18% MAX 50%

Lum

inan

ce (c

d/m

2) in

the

mes

opic

rang

e &

park

ing

desi

gn c

riter

ia

Comm max

Resid min

Moon

Mesopic range & walkway criteria

the mesopic luminance range, with luminances associated with 7%, 18% and 50% reflective surfaces, for moonlight, as well as the very darkest roadway point and very brightest roadway point luminances, for meeting IESNA DG-5-94 criteria for walkway lighting0.001

0.01

0.1

1

10

Walk 7% Area 18% MAX 50%

Lum

inan

ce (c

d/m

2) in

the

mes

opic

rang

e &

w

alkw

ay d

esig

n cr

iteria

Comm max

Resid min

Moon

Reaction time: mesopic & peripheral

l reaction time studies show that visual performance varies under different sources

l comparisons of reaction times to a peripheral detection task show that it takes one-sixth as much MH as HPS for the same “reaction time”

Reaction time: part of the visual task

l the driving visual task can be described as:– detection: can be peripheral or foveal, followed by

“looking at” what’s detected– recognition: ALWAYS a foveal visual task, based

principally on visual information – response: AASHTO allows 2.5 sec. for total

response time for SSDl lighting should provide for foveal visibility for

roadways (and parking lots?)l remember that headlights help

Reaction Time: “1/6th as much MH”

Reaction Time: “how much longer”

Reaction Time: “how much longer”

l comparison for same luminance level shows difference in reaction times of 0.1 to 0.3 sec

l using the AASHTO calculation for SSD, the difference in SSD for 0.1 sec is about the same as slowing down by 0.5 miles per hour

l the difference in SSD for 0.3 sec is about the same as slowing down by 1.5 miles per hour

l maybe slowing down (not speeding) is better than using reduced (inadequate?) light levels

& other SPD-related interactions

l visual acuity and S/P ratio of sourcel glarel aging and the size of the pupil l aging and the yellowing of the lensl transient adaptation

l and now we learn ..

RGCs, Melanopsin & Human Health

l very recent discoveries connect some retinal ganglion cells (RGCs) to control of melatonin, a hormone controlling the body’s diurnal cycle

l stimulation of melanopsin in RGCs suppresses melatonin and disrupts the diurnal cycle– this is associated with increased risks of some

cancers and conditionsl So RGCs are non-visual photoreceptors, with

melanopsin and its distinct spectral sensitivity– corresponds closely to “blue sky” radiation

Melanopsin & sensitivity functions

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

360 400 440 480 520 560 600 640 680 720 760wavelength (nm)

SPD: Incandescent (CIE A, 2856K)

0

0.0005

0.001

0.0015

0.002

0.0025

0.003

0.0035

360 400 440 480 520 560 600 640 680 720 760

SPD: High Pressure Sodium

0

0.001

0.002

0.003

0.004

0.005

0.006

0.007

0.008

0.009

0.01

360 400 440 480 520 560 600 640 680 720 760

SPD: Metal Halide

0

0.002

0.004

0.006

0.008

0.01

0.012

360 400 440 480 520 560 600 640 680 720 760

SPD: Fluorescent - 30003000K to 65006500K

0

0.002

0.004

0.006

0.008

0.01

0.012

0.014

0.016

0.018

360 400 440 480 520 560 600 640 680 720 760

Melanopsin evaluation of sources

Source Watts PhoLms ScoLms Mels

Equal Energy 0.56 100 235 0.14B65 0.53 100 255 0.16C_D 0.49 100 257 0.15C_A 0.61 100 147 0.07HPS from 0.25 100 66 0.02

to 0.26 100 70 0.03MH from 0.30 100 155 0.08

to 0.32 100 184 0.10F30 0.28 100 131 0.06F35 0.29 100 151 0.07F41 0.30 100 169 0.08F65 0.32 100 227 0.12

Atmospheric scatter & light pollution

l to evaluate skyglow we need to?l estimate the reflectance of the sky

– first-order estimate, includes most significant effect– based on Rayleigh scattering by atmosphere– this is what makes the daytime sky look blue and

the colors of the sunrise/sunset “properly” ordered– other scatter occurs and can create local effects– other atmospheric interference occurs (pollution)– for clear sky conditions, Rayleigh is the dominant

scattering and appropriate starting point

Rayleigh Scatter Index (RSI)

l Rayleigh scatter is directly dependent on:– quantity of radiation at a given wavelength– inverse fourth power of that wavelength

l RSI(λ) = k * S(λ) * (1/λ)4 summed over spectruml indicates the “relative probability for scattering”l over billions of photons and gas particles,

probabilities become appropriate first estimatesl RSI(λ) estimates the SPD’s reflected by the sky

– valid in relative terms, for comparisons only

Atmospheric scatter of sunlight

0

0.0005

0.001

0.0015

0.002

0.0025

0.003

0.0035

0.004

360 400 440 480 520 560 600 640 680 720 760

wavelength (nm)

Atmospheric scatter & light pollution

Blackbody radiation sunlight (6500K) hasx = 0.31 y = 0.32

scattered radiation per RSI estimate has x = 0.23 y = 0.22

Atmospheric scatter of incandescent

0

0.0005

0.001

0.0015

0.002

0.0025

0.003

0.0035

0.004

360 400 440 480 520 560 600 640 680 720 760

wavelength (nm)

RSI evaluation of sources

Source Pho Sco Mel RSI RSIpho RSIsco RSImel

Equal Energy 100 235 0.14 4.4 5.4 19.6 1.5B65 100 255 0.16 4.6 5.5 21.4 1.7C_D 100 257 0.15 3.8 5.5 21.4 1.6C_A 100 147 0.07 2.3 4.9 10.9 0.6HPS from 100 66 0.02 1.2 4.4 4.5 0.2

to 100 70 0.03 1.2 4.5 4.8 0.2MH from 100 155 0.08 2.3 5.0 11.9 0.8

to 100 184 0.10 2.5 5.2 14.4 1.0F30 100 131 0.06 1.7 4.9 9.5 0.5F35 100 151 0.07 1.8 5.0 11.4 0.7F41 100 169 0.08 2.0 5.1 13.0 0.8F65 100 227 0.12 2.5 5.4 18.6 1.2

Summary of evaluations of sources

Sources Pho Sco Mel RSI RSIph RSIsc RSImel

C_A 100 147 0.07 2.3 4.9 10.9 0.6AvgMH 100 166 0.09 2.4 5.1 12.9 0.90AvgHPS 100 68 0.03 1.2 4.4 4.6 0.24F30 100 131 0.06 1.7 4.9 9.5 0.5F35 100 151 0.07 1.8 5.0 11.4 0.7F41 100 169 0.08 2.0 5.1 13.0 0.8F65 100 227 0.12 2.5 5.4 18.6 1.2

Summary of evaluations of sources

Ratios for pairs of sources

Sources Pho Sco Mel RSI RSIph RSIsc RSImel

AvgMH /AvgHPS 1.0 2.4 3.4 2.0 1.2 2.8 3.8

C_D /C_A 1.0 1.7 2.3 1.6 1.1 2.0 2.6

F65 /F30 1.0 1.7 2.2 1.5 1.1 2.0 2.3

Conclusion: lots of consequences

l the benefits of SPD such as light and color, color rendering, color contrast and safety

l have associated characteristics such as LLD, lamp life, economics, energy use & pollution

l such as mercury pollution through productionof both lamps and power

l SPD’s also have complex interactions with vision, human health and light pollution

l so consider the consequences of that SPD

for a copy of this presentation, email: keithd@resodance.com

for links to more information about topics discussed in this presentation:http://resodance.com/ali/spectral.html

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