task - surround - ambient lighting

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___________________________________________

Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation.

Task – Surround –Ambient LightingPeter Ngai, PE, LC, FIESAcuity Brands Lighting

April 27th, 2016

Abstract:Task –Ambient lighting provides energy saving but space surrounding the users can be dim and uninviting. This study researched into the proposal of an additional Surround Layer of light. That is, Task-Surround-Ambient system. It examined in a simulated environment, illumination requirements, dimensionality and appearance of the space by the use of Vector/Scalar and Task/Vertical Illumination Ratios. They were evaluated under several illuminance requirements, different Task-Surround proportion combinations and various sources sizes of Surround Light. The results showed that by adding a Surround Light Layer, visual quality of space surrounding the users can be enhanced. Energy savings were also valuated under various illuminance conditions and physical layouts. They showed that Task-Surround-Ambient system achieves energy savings.

LEARNING OBJECTIVES:

Identify the strength and weaknesses of Total Ambient and Task-Ambient Lighting, and introduce the concept of Task- Surround – Ambient Lighting

Create an analytic model and introduce the lighting metrics for lighting comparisons

Compare Lighting Quality of Total Ambient, Task-Ambient and Task- Surround – Ambient Lighting

Compare Energy Savings for Total Ambient, Task-Ambient and Task- Surround – Ambient Lighting

Practical implementations of Task- Surround – Ambient Lighting

Lighting quality: glare-free & uniformly illuminated, reduced dimensionality and personalization

40 fc total @ desktop

Ambient Lighting

40 fc from ambient lighting

Lighting quality: low energy costs with high horizontal workplane illumination, but lower visibility of vertical elements or faces, less dimensionality and sharper shadows. Space rendered dingy and uninviting

Low Ambient –Task Lighting

30 fc from task lighting

10 fc fromAmbient lighting

40 fc total @ desktop

Lighting quality: added layer of surround light for dimensionality and interaction. Enhance the visual quality of the immediate space surrounding the users

SURROUND LIGHTING

10 fc from Ambient lighting

40 fc total @desktop

Low Ambient –Surround –Task lighting Solution

30 fc from surround +Task lighting

This Presentation is a conceptual comparison of Task –Surround –Ambient Lighting System

to Total Ambient and Task-Ambient Lighting Systems

In a Simulated Environment

The Analytic Model

Room Size: 32’ X 32’X 10’ 80%, 50% and 20% reflectancePersonal Space: 8’X 8’X5’ a work station in the middle of the room Task Area : 4’ diameter and 2.5’high with 50% reflectance circular table

Light sources: 4” X 4” diffuser panels for all three separate layers of lighting. Luminous intensity level for each layers adjusted separately

Ambient Lighting Layer -225 panels spaced evenly Surround Lighting Layer - 2’x2’ grid of 25 diffusers at 6’ height over the desk Task Lighting Layer - 21 diffusers mounted at 6” above the task surface It should be understood that the use of 4” X 4” luminous panels and the layouts of the panels were to reduce the analytic complexity. The luminous panels for task lighting layer were treated as photometric entities, and not as solid objects.

Lighting Layouts

Ambient Lighting layer

Surround Lighting layer

Task Lighting layerTask Surface

5 FT

10 F

TPhysical Layout of the Simulated Space

6 FT

8 FT

Lighting Criteria

Low Ambient illumination = 100 Lux

Task illumination @ desktop = 400 Lux

Two location points were analyzed:

1st Point - 10 inches away from the edge of the table and 4ft-2in from the floor.

2nd Point - center of the space at the same height

Center Location PointSide Location Point

Physical Layout of the Simulated Space

20 in

Lighting criteria were evaluated by two factors:1)The ratio of Vertical Illumination @ two location points facing the center of

personal space to that of task surface illumination needs to be within a ratio of 1:3 or better. That is, lower than 1:3

2) The points need to have acceptable Vector/Scalar Illumination ratios 1> V/S <2

Lighting Criteria

Vector/Scalar Ratio Flow of Light Appearance

3.5 Dramatic Theatrical3.0 Very Strong Strong Contrast, Details not discernable

2.5 Strong Suitable for display, too harsh for faces

2.0 Moderately Strong Pleasant for distant face

1.5 Moderately Weak Pleasant for near faces

1.0 Weak Soft Lighting for subdued effects

.5 Very Weak Flat, shadow free lighting

Lighting Effects at Different Vector/Scalar Ratios

Note: Values within bracket should not be ranked in terms of desirability. It is a matter of personal preference/application. CR 1:3 or 1<V/S<2.0 should not be taken literally

(Dimensionality)

Let E(x) and E(-x) be the two opposing Illumination on the X axis E(y) and E(-y) be the two opposing Illumination on the Y axis E(z) and E(-z) be the two opposing Illumination on the Z axis

Then, ʽE(x) = E(x) - E(-x) is the Illumination Vector on the X axis

ʽE(y) = E(y) - E(-y) is the Illumination Vector on the Y axis

ʽE(z) = E(z) - E(-z) is the Illumination Vector on the Z axis

|E|= √(ʽE(x) 2 + ʽE(y)

2 + ʽE(z) 2 ) (1)

The Scalar Illumination Esr , Esr = |E|/4 + (~E(x) + ~E(y) + ~E(z) )/3 (2)

Where ~E(x) is the lesser of E(x) and E(-x)

~E(y) is the lesser of E(y) and E(-y)

~E(z) is the lesser of E(z) and E(-z)

From Equation (1) and (2), Vector/Scalar Ratio = |E|/ Esr

Magnitude of the illumination Vector,

Vector/Scalar Ratio Calculation

Scenario Ambient Layer

Surround Layer

Task Layer

Total Ambient (LUX) 1 400 0 0

Lighting Scenarios


Surround Layer

Task Layer

Task-Ambient (LUX) 2 100 0 300

Lighting Scenarios


Surround Layer

Task Layer

Task-Surround-Ambient

(LUX)

3 100 100 2004 100 150 1505 100 200 100

Lighting Scenarios


Surround Layer

Task Layer

Surround –Ambient (LUX) 6 100 300 0

Lighting Scenarios


Surround Layer

Task Layer

Total Ambient 1 400 0 0

Task-Ambient 2 100 0 300


3 100 100 2004 100 150 1505 100 200 100

Surround –Ambient 6 100 300 0

6 Lighting Scenarios

Results Analysis

Scenario 1E (x) 227 E (-x) 220 ʽE(x) 7 ~E(X) 220 E (x) 245 E (-x) 139 ʽE(x) 106 ~E(x) 139E (y) 212 E (-y) 227 ʽEy) -15 ~E(Y) 212 E (y) 196 E (-y) 207 ʽE(y) -11 ~E(y) 196E (z) 476 E (-z) 128 ʽE(z) 348 ~E(Z) 128 E (z) 445 E (-z) 104 ʽE(z) 341 ~E(z) 104

Vector (Mag) 348 E (Vert) 227 Vector (Mag) 357 E (Vert) 245Scalar 274 E(Horz) 400 Scalar 236 E(Horz) 400

V/S 1.27 CR 1.76 V/S 1.52 CR 1.63Scenario 2

E (x) 73 E (-x) 70 ʽE(x) 3 ~E(X) 70 E (x) 82 E (-x) 39 ʽE(x) 43 ~E(x) 39E (y) 70 E (-y) 71 ʽE(y) -1 ~E(Y) 70 E (y) 54 E (-y) 57 ʽE(y) -3 ~E(y) 54E (z) 120 E (-z) 110 ʽE(z) 10 ~E(Z) 110 E (z) 113 E (-z) 41 ʽE(z) 72 ~E(z) 41



E (x) 118 E (-x) 112 ʽE(x) 6 ~E(x) 112 E (x) 146 E (-x) 51 ʽE(x) 95 ~E(x) 51E (y) 118 E (-y) 115 ʽE(y) 3 ~E(y) 115 E (y) 70 E (-y) 73 ʽEy) -3 ~E(y) 70E (z) 453 E (-z) 115 ʽE(z) 338 ~E(z) 115 E (z) 163 E (-z) 49 ʽE(z) 114 ~E(z) 49



E (x) 142 E (-x) 132 ʽE(x) 10 ~E(X) 132 E (x) 178 E (-x) 56 ʽE(x) 122 ~E(x) 56E (y) 143 E (-y) 137 ʽEy) 6 ~E(Y) 137 E (y) 75 E (-y) 78 ʽEy) -3 ~E(y) 75E (z) 632 E (-z) 115 ʽE(z) 517 ~E(Z) 115 E (z) 184 E (-z) 52 ʽE(z) 132 ~E(z) 52








V/S 2.48 CR 1.75 Scalar 1.91 CR 1.37

Ambient 400 Surround 0 Task 0






Center Location Point Side Location Point

Data on Computations of Illumination, Contrast Ratio and Vector/Scalar Ratios for Task Surface Illumination of 400 Lux

1:1.8 1:1.61:4.9

1:3.9 1:2.7

1:2.8 1:2.2

1:2.3 1:1.8

1:1.8 1:1.4

1:5.5

What can we tell from the above results?

1:1.8 1:1.61:4.9

1:3.9 1:2.7

1:2.8 1:2.2

1:2.3 1:1.8

1:1.8 1:1.4

1:5.5

1:1.8 1:1.61:4.9

1:3.9 1:2.7

1:2.8 1:2.2

1:2.3 1:1.8

1:1.8 1:1.4

1:5.5

Why?

E2(X)E1(X)

E1(X) @ Side Location Pt >

E2(X) @ Center location Pt

Total Ambient and Task - Ambient

E2(X)E1(X)


E1(X) @ Side Location Pt >

E2(X) @ Center location Pt

Why?

SSS

1:1.8 1:1.61:4.9

1:3.9 1:2.7

1:2.8 1:2.2

1:2.3 1:1.8

1:1.8 1:1.4

1:5.5

E1(+X)

E2(+Z)

V/S @ Side Location Pt >

V/S @ Center location Pt

E2(-Z)

E2(-X) E2(+X)

Total Ambient and Task - Ambient

E1(-X)

E1(+Z)

E1(-Z)

ʽE(x) = E(x) - E(-x)

ʽE(z) = E(z) - E(-z)

|E|= √(ʽE(x) 2 + ʽE(z)

2 )

|E1| |E2|>

1:1.8 1:1.61:4.9

1:3.9 1:2.7

1:2.8 1:2.2

1:2.3 1:1.8

1:1.8 1:1.4

1:5.5

Why?

E1(+X)

E2(+Z)

V/S @ Side Location Pt

V/S @ Center location Pt

E2(-Z)

E2(-X) E2(+X)

Task-Surround -Ambient

E1(+Z)

E1(-Z)

ʽE(x) = E(x) - E(-x)

ʽE(z) = E(z) - E(-z)

|E|= √(ʽE(x) 2 + ʽE(z)

2 )

|E1| |E2|

Scenario Side Location Point Center Location Point3 Vector 14.84 33.81

Scalar 9.38 19.85V/S 1.58 1.70

4 Vector 17.98 51.71Scalar 10.59 25.73V/S 1.70 2.01

5 Vector 21.85 73.82Scalar 12.23 33.15V/S 1.79 2.23

6 Vector 29.07 116.13Scalar 15.20 46.90V/S 1.91 2.48

Total Ambient Vs Task - Ambient Lighting at 400 lux Task Surface Illumination


Ambient 400 Ambient 100Task 300

0

50

100

150

200

250

300

Vertical Illumination

Center Side


0.000.200.400.600.801.001.201.401.60

Vector/Scalar ratio

Center Side

Total Ambient Vs Task - Ambient Lighting at 400 lux Task Surface Illumination

• Total ambient lighting is better in meeting criteria than task- ambient lighting for both vertical illumination contrast and V/S ratios. This is typical general lighting system that normally found in an open office or a classroom.


050

100150200250300


Center Side


0.00

0.50

1.00

1.50

2.00

Vector/Scalar ratio

Center Side

•Task – ambient lighting appeared to be dingy and dark. The contrast ratios is well below 3:1. While the V/R ratio for the side location point is acceptable, the low illumination renders the condition to be uninviting and dark.


Ambinet 100Surround 300

0

50

100

150

200

250

300

350Vertical Illumination

Center Side


Ambient 100 Surround 300

0.00

0.50

1.00

1.50

2.00

2.50

3.00Vector/Scalar Ratio

Center Side

Total Ambient Vs Task-Ambient Vs Surround- Ambient at 400 lux Task Surface Illumination



Ambinet 100Surround 300

050

100150200250300350 Vertical Illumination

Center Side


Ambient 100 Surround 300

0.000.501.001.502.002.503.00 Vector/Scalar Ratio

Center Side

Total Ambient Vs Task-Ambient Vs Surround- Ambient at 400 lux Task Surface Illumination

• The vertical illumination was high and well within the 1:3 contrast ratio. This resulted in brightening up of the entire personal space.

• V/R ratios were high. it drastically increased the dimensionality. In fact, some individuals might find V/S ratio of 2.5 at Center Location Position as too high.

• Side Location point has higher Vertical Illumination and low CR.

Amb 400Sur 0Tsk 0

Amb 100Sur 0

Tsk 300

Amb 100Sur 100Tsk 200

Amb 100Sur 150 Tsk 150

Amb 100 Sur 200Tsk 100

Amb 100Sur 300

Tsk 0

0

50

100

150

200

250

300


Center Side

Lighting comparisons for Surround Lighting Layer @400 Lux Task Surface Illumination for different ambient/surround/task light levels


Amb 400Sur 0Tsk 0

Amb 100Sur 0

Tsk 300




Amb 100Sur 300

Tsk 0

0

50

100

150

200

250

300

350


Center Side


•The higher was the surround light contribution, the higher was the vertical illumination•Contrast ratios from all combinations were better than 1:3 once the combination of Ambient/Surround/Task ratio reached 100/100/200

Amb 400Sur 0Tsk 0

Amb 100Sur 0

Tsk 300




Amb 100Sur 300

Tsk 0

0.00

0.50

1.00

1.50

2.00

2.50

3.00

Vector/Scalar Ratio

Center Side



Amb 400Sur 0Tsk 0

Amb 100Sur 0

Tsk 300




Amb 100Sur 300

Tsk 0

0.00

0.50

1.00

1.50

2.00

2.50

3.00

Vector/Scalar Ratio


• v/s ratios from all combinations were between 1 and 2 once the combination of Ambient/Surround/Task ratio reached 100/100/200.

• Contrast ratios moved higher as surround lighting contribution increases.

• The results showed that with a wide range of adjustments for task and surround lighting layers, a user could achieve a satisfactory lighting condition for his/her preference.

Effect of Task Surface Illumination Levels

Amb 200Sur 0Tsk 0

Amb 100Sur 0

Tsk 100

Amb 100Sur 33Tsk 67

Amb 100Sur 50Tsk 50


Amb 100Sur 100

Tsk 0

020406080

100120140160

Center Side

Amb 400Sur 0Tsk 0

Amb 100Sur 0

Tsk 300




Amb 100Sur 300

Tsk 0

0

50

100

150

200

250

300

350Vertical Illumination

Center Side

What can we tell from the

results?

400 Lux

300 Lux 200 Lux


Amb 200Sur 0Tsk 0

Amb 100Sur 0

Tsk 100

Amb 100Sur 33Tsk 67

Amb 100Sur 50Tsk 50


Amb 100Sur 100

Tsk 0

020406080


Center Side

Amb 400Sur 0Tsk 0

Amb 100Sur 0

Tsk 300




Amb 100Sur 300

Tsk 0

0

50

100

150

200

250

300


Center Side

• Trends for CR were the same as that at 400 lux. The higher was the surround lighting portion, the higher was the vertical illumination and V/S ratio.

• For scenarios involving surround lighting layer, similar to 400 lux task surface illumination case, the side location points had higher vertical illumination.

• When comparing across task surface illumination levels, the lower was task surface illumination, the more the values moved towards compliance. The reason was that at lower surface illumination level, Ambient Lighting Layer that was held to a constant value, contributed a larger proportion of the total task surface illumination.

400 Lux 300 Lux 200 Lux

300 Lux


Amb 200Sur 0Tsk 0

Amb 100Sur 0

Tsk 100

Amb 100Sur 33Tsk 67

Amb 100Sur 50Tsk 50


Amb 100Sur 100

Tsk 0

0.0

0.5

1.0

1.5

2.0

2.5

Center Side

Amb 400Sur 0Tsk 0

Amb 100Sur 0

Tsk 300




Amb 100Sur 300

Tsk 0

0.0

0.5

1.0

1.5

2.0

2.5

3.0Vector/Scalar Ratio

Center Side

What can we tell from the results?

400 Lux

200 Lux


• When comparing across task surface illumination levels, the lower was task surface illumination, the more C/S values moved towards compliance. The reason was the same as Vertical Illumination

Amb 400Sur 0Tsk 0

Amb 100Sur 0

Tsk 300




Amb 100Sur 300

Tsk 0

0.0

0.5

1.0

1.5

2.0

2.5

3.0

Amb 200Sur 0Tsk 0

Amb 100Sur 0

Tsk 100

Amb 100Sur 33Tsk 67

Amb 100Sur 50Tsk 50


Amb 100Sur 100

Tsk 0

0.0

0.5

1.0

1.5

2.0

2.5

VECTOR/SCALAR

• All 3 combinations of Ambient /Surround/Task location points for all three light levels within the acceptable range both in terms of Illumination Contrast Ratios and V/S ratios.

• Trends in V/S same as that at 400 lux. The higher was the surround lighting, the higher was V/S.

• Similar to 400 lux task surface illumination case, the side location points had lower V/S ratio.

• The results showed that the concept of Task-Surround-Ambient worked for a wide range of task surface illumination.

Effect of Surround Lighting Layer Size

Vertical IlluminationSide Location Point

Vertical IlluminationCenter Location Point


Equal Light Output

E1(X) E2(X)

E1(X) < E2(X)

Vertical Illumination Center Location Point

For center point location, Larger size, greater Vertical Illumination, why?

Equal Light Output

E1(X) E2(X)E1(X) ≈ E2(X)

Vertical Illumination Side Location Point

Side point location, different sizes, similar Vertical Illumination, why?


Vertical IlluminationSide Location Point

Vertical IlluminationCenter Location Point

• For center location point, the larger was the size of surround light source, the greater was the vertical illumination.

• For side location point, different surround light source sizes did not affect Vertical Illumination appreciably.

• For center location point, the more surround light, the more was the vertical illumination.

• For side location point, the more is surround light, the greater was the vertical illumination.



Vector/Scalar RatioCenter Location Point

Vector/Scalar RatioSide Location Point

Equal Light Output

E1(Z) E2(Z)

V/S(1) > V/S(2)

E1(Z) > E2(Z)

Vector/Scalar Ratio Center Location Point

For center point location, smaller size, greater Vertical Illumination, why?

Equal Light Output

E1(Z)E2(Z)

E1(Z) ≈ E2(Z)

V/S(1 ≈ V/S(2)

Vector/Scalar Ratio Side Location Point

Side point location, different sizes, similar Vertical Illumination, why?


Vector/Scalar RatioCenter Location Point

Vector/Scalar RatioSide Location Point

• For center location point, the smaller was the area of the Surround Lighting layer, the higher was the V/R ratio.

• For center location point, the more was surround light, the greater was the V/R ratio.• For side location point, different surround light source sizes did not affect V/R appreciably.

• For side location point, the more surround light, the greater was the V/R ratio.


1. Smaller surround light size, creates greater luminance and high V/R ratio. This produces glary, hash and dramatic lighting environment. Not a good approach for surround lighting layer. As the surround source size increases, luminance intensity reduces and the environment gets softer and more comfortable.

2. Results and assertions from task surface illumination of 400 lux can be extended to lower task surface illumination level. When the overall task surface illumination is lowered, the proportion of ambient lighting layer contribution to task surface illumination increases. This will pull the results closer to that of the ambient only system. Hence, at lower task illumination, various sizes of Surround Lighting Layer will behave similarly to that of at 400 lux and with more ease of compliance.

5, 9 and 12-Stations Layout

Relative Energy Consumptions



Amb 400

Sur 0Tsk 0

Amb 100

Sur 0 Tsk 300

Amb 100Sur 100Tsk

200



Amb 100Sur 300

Tsk 0

Amb 300

Sur 0Tsk 0

Amb 100

Sur 0 Tsk 200

Amb 100

Sur 67Tsk 133


Amb 100 Sur 133

Tsk 67

Amb 100Sur 200

Tsk 0

Amb 200

Sur 0Tsk 0

Amb 100

Sur 0 Tsk 100

Amb 100

Sur 37Tsk 67

Amb 100

Sur 50 Tsk 50

Amb 100

Sur 67Tsk 33

Amb 100Sur 100

Tsk 0

0.00

0.20

0.40

0.60

0.80

1.00

1.20

5 Workstations 9 Workstations 12 Workstations

400 lux 300 lux 200 lux


• As the proportion of surround light increased, the energy savings decreased.

Amb 400

Sur 0Tsk 0

Amb 100

Sur 0 Tsk 300

Amb 100

Sur 100Tsk 200

Amb 100

Sur 150 Tsk 150

Amb 100

Sur 200Tsk 100

Amb 100

Sur 300Tsk 0

Amb 300

Sur 0Tsk 0

Amb 100

Sur 0 Tsk 200

Amb 100

Sur 67Tsk 133

Amb 100

Sur 100 Tsk 100

Amb 100

Sur 133Tsk 67

Amb 100

Sur 200Tsk 0

Amb 200

Sur 0Tsk 0

Amb 100

Sur 0 Tsk 100

Amb 100

Sur 37Tsk 67

Amb 100

Sur 50 Tsk 50

Amb 100

Sur 67Tsk 33

Amb 100

Sur 100Tsk 0

0.000.200.400.600.801.001.20

5 Workstations 9 Workstations 12 Workstations400 lux 300 lux 200 lux

• Total Ambient Lighting had the highest energy consumption for all three workstation layouts and all lighting scenarios. Task – Ambient Lighting consumed the least.

• The higher was the task surface illuminance, the higher was the relative energy savings. This was true for all lighting scenarios.

• The lower was the density of workstations, the higher was the energy savings. • Energy savings for Task-Surround-Ambient lighting system compared favorably with Task-Ambient

system. This was especially true in case of high task surface illumination and low density workstation layout.

Implementing Low Ambient –Surround –Task lighting Solutions

• The addition of surround lighting layer is effective in enhancing dimensionality and the appearance of space over and beyond what Task-Ambient Lighting can offer.

• This is valid though a range of task surface illumination and surround light source sizes.

• The study also taught the idea of adjusting to different combinations of Task and Surround Lighting Layers which allows the user to tune to for different lighting applications as well as personal preferences.

• This study showed energy savings for Task- Surround – Ambient Lighting compared favorably to that of Task-Ambient Lighting system.

Conclusions

• The study was anchored with two lighting measures. illumination ratio and the Vector/Scalar Ratio The first criterion is straight forward and generally accepted. As for the second criterion, there are a number of other models including, Cylindrical /Horizontal Illumination Ratio, Vector/Cylindrical Illumination Ratio and Target/Ambient illumination Ratio (TAIR) among others. Vector/Scalar Ratio is probably the most recognized metric. Hence this study adopted this criterion. While other metrics will yield different numeric results, but the essences and trends investigated by this study using Vector/Scalar should be similar.

• This study was based on a specific set of lighting conditions. Different sets of input will not replicate identical numeric values. However, this should not alter the fundamental results and conclusions of this study. The main trust of this paper is to gain insight of the interplay among the three layers of light. Hence, the study should be viewed in a conceptual perspective rather than quantitative precision. When a specific lighting layout is known, then the lighting can be evaluated for that specific condition.

Discussions

• The results of this paper is not limited to facial modeling. It is valid to extend to appearance of any objects within the personal space. Hence Task - Surround concept is just as applicable with multiple persons interacting within the space, as with a single person working in solitude.

• It is important to point out that this study focused on the visual appearance surrounding the task area by means of Contrast Ratio and Vector/Scalar Ratio. Other important lighting quality factors such as task visibility, visual comfort, and health and wellbeing aspects though not the subject of our study, should always be considered.

• Final, while the study was done with three discrete layers of lighting for clarity, in practice, it is conceivable that one luminaire through its light distributions and positioning, can function as more than one layer of light.

Discussions

Thank You

task - surround - ambient lighting

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