11/14/2016 Exponation AIA Provider Number: 70119700 Meters, - - PDF document

11/14/2016 1

Exponation

AIA Provider Number: 70119700

Meters, Metrics and Visual Perception

LEDSSMW16-S#1

Kevin Willmorth, Lumenique LLC and Tasca

11.15.16 Credit(s) earned on completion of this course will be reported to AIA CES for AIA members. Certificates of Completion for both AIA members and non-AIA members are available upon request. This course is registered with AIA CES for continuing professional

• education. As such, it does not

include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction

• r any method or manner of

handling, using, distributing, or dealing in any material or product.

_______________________________________ Questions related to specific materials, methods, and services will be addressed at the conclusion

• f this presentation.

This presentation will explore the issues

• f metrics, meter use and the connection

and disconnect these have with actual visual results. The exploration includes presentation of a concept for a more complete metric representation of lighting qualities, the combines uniformity, color and visual qualities.

Course Description Learning Objectives

• 1. Understand the use of metrics and their

limitations, and how to use them to solve real world issues, while avoiding assumptions about them that lead to issues in application.

• 2. Understand how meters used to evaluate

products and field results work, where they can be relied upon, and when they produce unreliable data. Includes presentation of simple strategies for gaining the best meter results, and what meters on the market today can do for designers.

• 3. Gain insight into the potential of creating a new

metric tool for evaluating products, built from information already available. See how this can be done without manufacturer participation or a single committee meeting, by building a basic spreadsheet based evaluation tool to qualify products. The spreadsheet master will be made available to all who attend.

• 4. See how visual perception and accommodation

to lighting conditions amplifies some problems, while erasing others, and using this to prioritize in the design process.

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Finding the happy medium between cost and result

In this presentation we will…

• Walk through a little background on light metering
• Review affordable and practical metering approaches
• Explore how meters can be used in field application
• Talk about tools and accessories to improve the metering

experience

• Discuss common metering errors and approaches to improve

results

• Look at a method for classifying products based on metered

results and catalog data, or both

Metrics vs. Vision

The human visual system has zero accuracy – cannot be calibrated to a known standard

Variable, uncalibrated optical receiver parts with adaptive features that change with age Variable software with “subjective” perception feature that changes with age

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Non Linear Perception

• Human perception of brightness not linear
• Person to person perception is not uniform

100 95 90 85 80 75 70 65 60 55 50 45 40 35 30 25 20 15 10 5 100 97 95 92 89 87 84 81 77 74 71 67 63 59 55 50 45 39 32 22 10 20 30 40 50 60 70 80 90 100 100 95 90 85 80 75 70 65 60 55 50 45 40 35 30 25 20 15 10 5 Measured Light Percieved Light

Relative Illuminance Relative Power Level

Non Linear Visual Performance Response

• Human response to spectral color balance is not flat
• Varies by age, health, and individual preference

CCT S/P Ratio EVE Factor Perceived Illuminance (20Fc Base) 2700K 0.8 1.56 12.82 3000K 1.25 1.09 18.35 3500K 1.4 1.00 20.00 4000K 1.6 0.90 22.22 5000K 2.0 0.75 26.67

Subjectivity Filter

It’s too dark in here Wrong, too bright, I can still see you

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So We Invented Meters

• Changes observation from subjective (looks good) to
• bjective (numeric value)
• Allows metric comparison
• Between observers
• Over time
• Calibration = verifiable accuracy

Electrophot 1931 Weston 617 1932

Why Meter

• Evaluate a product
• Survey a lighting condition
• Verify performance against a product specification
• Verify performance against a calculated prediction
• Monitor performance over time (color)
• Track lumen depreciation
• Evaluate an environment to be lighted
• Solve problems or capture design data
• Understand more about light in a space

Testo 540

What We Meter

• Illuminance
• Color and color characteristics
• Modulation (Flicker)
• A wide range of pecific

applicable characteristics

• Brightness (luminance)
• X-y coordinate
• Duv shift
• Etc…

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Data Extrapolated from Readings

• Color Accuracy
• CRI Ra and specific R values
• TM30 Rf and Rg
• MacAdam Steps from standard center point
• Visual performance
• Human factors
• Energy vs. Power
• Consistency comparison
• S/P ratio
• Horticultural
• PPFD (Photosynthetic Photon Flux Density)
• PAR (Photosynthetic Active Radiation)

Factors, Approaches and Meters in Use

Factoring Required for Visual Response

• Need to match meter response to human visual response
• Otherwise, meter is just measuring total energy collected at the

photo receptor or cell, whether or not it can be “seen”

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Cosine Correction for Illuminance

• Cosine correction for illuminance measurements
• Does not provide luminance or spot measurement

Lambert’s cosine law

Accuracy vs. Precision

• Accuracy is how close a meter will produce a result against a

known reference or standard

• Older meters are +/- 10% of any reading
• Newer meters are +/- 5% Illuminance, +/-.003 in x-y, +/-3% CCT
• Precision is how tight readings are to one another, sometimes

referred to as repeatability

• Older meters are +/- 5%
• Newer meters are +/- 2% Illuminance, +/-.0015 in x-y, +/-1% CCT
• Look for values that are < 50% of accuracy specification
• Accuracy range: Reading vs. Full scale
• Full scale is % of max reading (not good)
• Reading is % of any reading (good)

Analog Meters

GE DW-48 1940 GE DW-58 1946 GE 217 1990 GE 214 1960

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Essentially Voltmeters and Photocells

0.980 0.985 0.990 0.995 1.000 1.005 2700 3500 5000 Relative Measurement

CCT of Light Source

Meter No Filter Green Filter

Silicon Photocell Response Green Filter Results Volt Meter and Silicon Photocell

LED Light and Analog Meters

Selenium photocell not suited to measuring illuminance under LED sources If it doesn’t use a battery and an analog gage, it may have issues

Low Cost Digital Meters

Diffuser (Cosine Corrector) Gage (Voltmeter w/firmware) Photosensor (under diffuser) Calibration using varistor and firmware – calibrated for all light sources and daylight Detachable sensor head is an excellent feature Amprobe LM-200LED Hundreds of similar meters from $50 to $1200

11/14/2016 8

Quality Digital Meters

Detachable sensor head Array of multiple sensors Minolta TM-10

Other Useful Meters

Many older digital light Meters – from fluorescent era forward Check against a known modern meter to verify Photographers light meters

• with spot attachment

Minolta T-1H Minolta AM-4F Minolta CM-2

Meter LED Error

Vs. Vs. Vs.

2700K 3000K 3500K 4000K 5000K DW58 10 22 32 45 60 LM-200LED 84 84 84 84 84 Minolta T-1H 83.7 84 85.1 84.1 84 GE 214 45.5 47 50 50 50 10 20 30 40 50 60 70 80 90 Illuminance

11/14/2016 9

Meter LED Error

Vs. Vs.

2700 K 3000 K 3500 K 4000 K 5000 K LM-200LED Lo 74 82 83 87 90 GE217 Lo 51 51.5 51.5 52 52 GE 214 Lo 49 48 50 50 50 10 20 30 40 50 60 70 80 90 100 Illuminance

Lo Light

2700 K 3000 K 3500 K 4000 K 5000 K LM-200 Hi 349 382 383 406 415 GE217 Hi 220 190 210 210 220 GE214 Hi 240 250 240 245 240 50 100 150 200 250 300 350 400 450 Illuminance

Hi Light

Old School Modular Scientific Meters

Multiple detachable detectors Various remote and attached sensors Electronics- readout per attached head Calibration using firmware and varistor at gage with filters depending in attachment Tektronix

Modern Spectral Light Meter – App Base

Diffuser (Cosine Corrector) Software driven gage and readout Multiple spectral sensor Calibration using software Detachable sensor head Assensetek Lighting Passport

11/14/2016 10

Modern Meter Delivered Results

CCT CRI(Ra)(R1-R8) Re(R1-15) R1~R15 CQS Illuminance Foot Candle CIE 1931 CIE 1976 Spectrum Diagram C78.377-2008 IEC-SDCM TM-30-15(Rf, Rg & Diagram) Peak Wavelength (λp) Dominant Wavelength (λD) Purity Duv SP Ratio PPFD (380~780 nm) Flicker Frequency(5-200 Hz) Flicker Percentage Flicker Index Temperature Relative Humidity

90 Parameters

Modern Meter Computer Interface

CCT CRI(Ra)(R1-R8) Re(R1-15) R1~R15 CQS Illuminance Foot Candle CIE 1931 CIE 1976 Spectrum Diagram C78.377-2008 IEC-SDCM TM-30-15(Rf, Rg & Diagram) Peak Wavelength (λp) Dominant Wavelength (λD) Purity Duv SP Ratio PPFD (380~780 nm) Flicker Frequency(5-200 Hz) Flicker Percentage Flicker Index Temperature Relative Humidity

Desktop software evaluation tools

Integrated Meters

UPRTek Minolta CL70 Minolta CL500 Gigahertz Optic Metrue Sim-2

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Lab Meters – PC Connected

For fixed installations Mightex CCD Spectrometer Ocean Optics Jaz

Meters Reviewed

See review and summary of 9 meters at: Lumeniquessl.com

http://wp.me/pnP76-tm

Modern Meter Accuracy Comparison

Vs. <$100 Illuminance Only >$2,000 Illuminance + 89 other Parameters Meters do not need to be expensive to be precise and accurate

210 215 220 225 230 235 240 245 250 255 260 2700K 3000K 3500K 4000K 5000K Illuminance LED CCT

Meter Comparison

>$2000 <$100 All readings within +/- 0.98%

11/14/2016 12

Meter Accuracy Comparison

Vs. Analog meters disagree by >24% to one another

Assensetek LM-200LED Minolta T1H GE 214 GE 217 Incand 36.6 36.1 36.4 29 22 Error Base 1.4% 0.5% 20.8% 39.9% Assensetek LM-200LED Minolta T1H GE 214 GE 217 5000 LED 40.1 39.6 39.9 30 22 Error Base 1.2% 0.5% 25.2% 45.1%

Vs. Vs. Vs.

Color Meter Error

• 600
• 500
• 400
• 300
• 200
• 100

2700 3000 3500 4000 5000

Color Deviation from Published LED CCT

Assensetek Mightex Minolta CM2 Low Minolta CM2 High

Vs. Vs. Older photographic color meters are not calibrated to accurately read LED CCT

When and Why a New Meter

• All analog meters should be discarded
• Replace color meters not designed to include LEDs specifically

in specifications

• Repair and or replace meters out of calibration
• Replace old cheap meters after 5 years +/-
• Have quality meters calibrated every 1-3 years depending on use
• New meters deliver valuable data
• Color
• Flicker
• Calculated factors, software connection, data output, etc.
• Separation of sensor head from instrument
• When a meter produces results that are inconsistent or

suspicious

• Reading to reading should be within 1-5% of new reference

11/14/2016 13

Beyond the basic function of illuminance on a desktop

Photometric

• Meters reading Fc or Lux can be used to

generate candela data for comparisons and evaluation

Distance “D” (25’ or 7.62M) Candela = Fc x D² (in feet) Lux = Fc x D² (in meters) Align meter normal to incident angle 12Fc x 25² = 7,500cd 129.17Lux x 7.62² = 7,500cd 12Fc 129.17Lux 55°

Transmission

Transmission = FC or Lux through material / FC or Lux no material Align meter normal to incident angle Fc through material = 112Fc Fc without material = 238Fc 112/238 = 47% Transmission Align material normal to incident angle and close to meter sensor

11/14/2016 14

Reflectance

Reflectivity = FC or Lux off material (A) / FC or Lux direct (B) Align meter normal to incident angle Fc off material = 112Fc Fc direct = 238Fc 112/238 = 47% Reflectance Distance A+C and B+C must be identical A B C Incident and reflected angles should match

Simple Benchtop Goniometer

Mount for small fixtures/lamps Rotate in X axis in any degree steps desired with controller

• r manual crank

Mount any illuminance meter here Can be also be done with two tripods, protractor and string

Larger Simple Lab Setup

Benchtop Goniometer on steroids

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Special Lab Setups

Special purposes and comparison test rigs Exposure and transmission evaluation Small source tabletop goniometer

Relative Measurement

• Comparisons and ratios do not require absolute values
• Precision (repeatability) more important than accuracy
• Distance to subject and optics must be equivelant
• Comparison of a known reference source to another

A: Known good source Ref: 600lm Reads 36Fc 24” 24” Reads 30Fc 600/30 = 20 (Ratio of lumens per Fc measured) B: Comparison source Lumens??? 20 x 36 = 720lm (Source B relative lumens)

Applying Relative Measurement

Test Lumens Reading Multiplier Ref 322 157 2.051 Reading Multiplier Lumens Test 1 141 2.051 289.19 Test 2 172 2.051 352.77

Metric values are less important than ratios to reference source Light meter modified for use with sphere sensor Ref and Test sources must be of similar optical character

11/14/2016 16

Relative Spot Measurement

A B C D E F G

ID Ev Comp Ratio A 10.1 A:C 1.4:1 B 5.7 A:B 1.9:1 C 7.2 E:C 1.7:1 D 8.1 A:D 1.2:1 E 11.9 E:A 1.2:1 F 9.1 A:F 1.1:1 G 8.0 A:G 1.3:1

Metric values are less important than ratios between target surfaces Brightness ratio using a spot meter

Common Measurement Errors

• Incorrect assumptions about what meters can do
• Lack of care in setting up meter to capture measurement
• Inconsistent measurement location
• Inconsistent distance from source
• Lack of preparation for repeating measurements
• Interference from surrounding sources or reflective surfaces
• Mismatch between meter and light source
• Observer interference
• White shirt effect on illuminance
• Red shirt effect on color measurement
• Wrong meter setting
• Poor equipment condition and lack of calibration

Field Measurement for Repeatability

• Make a map of the space and note of conditions
• Establish a fixed x,y,z point that can be recaptured later
• Use a meter sensor mount vs. hand holding
• Tripod or monopod mount ideal
• Measure at night for artificial sources
• Measure without and without artificial light when measuring

daylight contribution

• Capture artificial at night to differentiate contributions clearly
• Make field holding tools and keep them handy

11/14/2016 17

Field Measurement for Repeatability

Accuracy here is critical in monitoring lumen depreciation over time

A few additional things to have in the tool bag

Handy Tools to Increase Accuracy & Precision

Monopod Tape Measure Level and Protractor or App Pocket Pointer String, tacks, tape Gray Card Color Checker Plans Tripod

11/14/2016 18

Handy Accessories for Test Setup

Black foil to make Masks Integrating Isolation Tube Tripod Adapter for Sensor Heads Hold sensor head to ¼ x 20 bipod or monopod stand Block light from surrounding when measuring single fixture

• utput

Isolate a single light source for relative measurement Laser Pointer Help in aligning and locating sensor

Reference Sources to Establish Baseline

A reference source can be anything that has good data behind it

• For casual non-lab use, a

good downlight with solid photometric file from a manufacturer can be used

• Mount it a set distance from

the meter

• Check 0°Nadir Candela by

reading Fc x D²

• The result should be within

10%

• If good, keep the light as a

reference for future meter checks and comparisons

Temperature Meter – Critical with LEDs

• Temperature Meter
• K type thermocouples
• Various contact types
• At least 2 channels
• Temperature has a great

impact on light output

Amprobe TMD-10 2 channel <$100 Reed SD-947 4 channel <$200

11/14/2016 19

Simple Flicker Meter

If you see flicker, it exists – the actual metrics won’t change that See description and review at: Lumeniquessl.com

http://wp.me/pnP76-wu

Electronic Flicker Meter

Understand what the metrics are and why they are meaningful See meter in use and review at: Lumeniquessl.com

http://wp.me/pnP76-CU

UPRTek 250N SVM Calculation Also CCT/Lux/CRI <$1000

A concept for multi-dimensional description of white lighting qualities

11/14/2016 20 The IP Model

Dust Water Impact IP

• Size of particle
• Environmental

(movement)

• 1-6 classification (6

highest)

• Size of object
• Impact energy
• 1-9 classification (8

highest)

• Volume of water
• Pressure/direction/immersio

n

• 1-8 classification (8 highest)

A standard delivering classification information with some depth

LQC – Lighting Qualities Classification

Uniformity Light Quality Human Factors LQC

• CCT Variation / COA
• Duv
• MacAdams Variable
• S/P Ratio
• Flicker
• Color Fidelity
• Saturation Effects
• Spectral Consistency

(lowest R value) Aggregate multi-dimensional quality classification 1-5 values – 5 highest

Uniformity

• Applied Metrics
• CCT Limits (variation from the stated value)
• Duv – Deviation above or below the Plankian locus
• MacAdam steps from center point of stated CCT value @

Plankian locus intersection

• Rating 1-5, based on combined results of values
• 1 delivers the least uniform performance
• 5 delivers optimal uniformity

11/14/2016 21

Quality

• Applied Metrics
• Average CRIe or TM-30 Rf
• Lowest specific “R” value included in average
• TM-30 Rg value
• Rating 1-5, based on combined results of values
• 1 delivers the lowest color quality
• 5 delivers optimal color performance and rendering

Human Factors

• Applied Metrics
• S/P Ratio
• Flicker rating (Frequency, % and Index combined)
• Rating 1-5, based on combined results of values
• 1 delivers the lowest visual performance
• 5 delivers optimal visual performance

LQC Metrics

Uniformity Classification Metric CCT Var Duv MacAdam 1 >250 >+/-.007 5 2 249-200 <+/-.007 4 3 199-150 <+/-.005 3 4 149-100 <+/-.003 2 5 <100 <+/-.002 2 Quality Classification Metric CRIe or TM30Rf Lowest Individual value TM30 Rg 1 <69 35 n/a 2 70-79 40 90-110 3 80-84 45 90-110 4 85-94 70 95-105 5 >95 90 99-101 Human Factors Metric S/P Ratio Flicker Freq Flicker % Flicker Index 1 <.89 <200Hz >30 >.10 2 .90-1.2 <200Hz <30 <.10 3 1.21-1.80 >200Hz <15 <.05 4 1.21-1.80 200-1999Hz <4 <.01 5 >1.81 >2000Hz n/a n/a

11/14/2016 22

Applied LQC Rating Examples

LQC-235

• Factory space with medium color demand, high visual

performance demands

• Places emphasis on economy and visual performance

LQC-33

• Budget specification with no human factors consideration

LQC-55

• High color performance for retail/museum

LQC-555

• Inspection task light for critical visual performance

Simple Workbook

More detail and download the workbook: Lumeniquessl.com

http://wp.me/pnP76-Dm

Color Viewer Used in Testing

More detail: Lumeniquessl.com

http://wp.me/pnP76-DH

• Cree LEDs
• All 90CRI
• 2700K
• 3000K
• 3500K
• 4000K
• 5000K
• Dimmable from

500Fc to 10Fc

11/14/2016 23

Happy Metering!

This concludes The American Institute of Architects Continuing Education Systems Course

Kevin Willmorth Lumenique, LLC www.lumenique.com 414-241-5124 kwillmorth@Lumenique.com