ldg-2 · rendering made by dialux evo square downlight with trapezoid beam (right) round downlight...

LdG-2 Lighting design Guide for Vertical Surfaces Ezzat Baroudi

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LdG-2 Vertical Illuminance

Introduction When I first started my career, I was told by many Engineers that light planning is only a matter of

calculation the light on working plane which is in most cases around 0.8m from floor level, which means

planning the light only for horizontal spaces!

Later I found out in most cases that light beams and scallops are more visible on vertical not horizontal

which would make vertical as important as horizontal if not more important!

For this guide the calculation and rendering was mad by DIALux evo software which is available as a free

software from www.DIALux.com

Light shape what is called light scalloping is very visible on wall and makes the vertical surfaces very important

during lighting design stage.

This guide will help you plan the lighting by having proper offset to achieve

1-Grazing light (light scalloping) by different beam and offset

2- Uniform grazing light

3- Uniform wallwashing

4-Accent for objects on wall

Grazing (light scalloping)

Grazing light might not be the best option but when it is made it should be made right without making odd

shape and destroying the space by weird light scalloping.

To avoid bad light scalloping first you should know the following:

1-The difference between round and square downlight


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2- The beam angle of the luminaire

3-The light distribution Quality (main beam and secondary beam)

4- The effect of light with different offset from wall(distance from wall)

5- The alignment of scallops with architectural lines.

6- Intensity of lighting scallops

7-LED Downlight with scallops.

The difference between round and square downlight The light scallop of a round downlight is different from a square downlight

Trapezoid beam of a square

downlight

Cone beam of around

downlight

Rendering made by DIALux evo

Square downlight with Trapezoid beam (right)

Round downlight with Cone beam (left)

It should be noted that downlight with lens will make the beam softer.


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Also a square downlight with round opening will have a cone beam

The Trapezoid beam will be produced when the downlight opening is square not

the housing or frame.

Cone beam of round downlight Trapezoid beam of a square downlight

The beam angle of the luminaire Different beam angle will have different scallop size on wall

From right to left

Narrow spot 5o

Spot 14o

Flood 28o

Wide flood 45o

The light distribution Quality (main beam and secondary beam) while many bad downlights or spotlights have lots of lines around the main beam angle there are

good downlights that have soft beam edges


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Downlight with many lines for

main and secondary beam

Downlight with soft beam edge

The beam and light distribution is produced by either lamp or Luminaire.

A reflector lamp without any additional optical system has different effect that lamp with additional

optical system.

QR-CB 51(MR16) 50 watt 10o in a

luminaire with additional Reflector

QR-CB 51 (MR16) 50 watt 10o in a

luminaire with trim only no reflector

Additional Reflector could improve the beam quality and make the light distribution better as could

be seen from above rendering after using the manufacture’s photometric data in I evo.

It should be noted that usually the main purpose of a luminaire reflector is to prevent glare and

improve the visual comfort, so it is not always you get better scalloping.


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Also using different reflector lamp with similar beam angle will produce completely different

scalloping

QR-51 50 W 12 V 10° GU5.3

(MR 16)

QR-111 50 W 12 V 6° G53

(AR-111)

Selecting the lamp and its optical system will make a big different scalloping result.

It is always good to check the luminaire in real mock-up and use the correct photometric to get the

same in reality.

I have experienced many cases where engineers calculate from one manufacture and use

specification of another one! , which could have completely different results.

Lighting software like I will get accurate results only if right inputs are used and the most important

parameter is selecting the right photometric.

The effect of light with different offset from wall(distance from wall)

The scallop size on wall will be affected also from the offset from wall (how far the center of

luminaire from wall).

Usually all offset when mentioned it means from center of luminaire, so in this Guide all offset are

from center of luminaire to wall.

The more offset from wall the lower the scallop from top of the wall as could be seen from bellow

rendering.


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150 mm produce scallop close to top of

wall 500 mm produce scallop lower will less

intensity than 150 mm offset

To avoid having different scalloping size in one room it is good to keep the same offset from walls

identical, having one offset from one wall different from another will make different scallops

When offset are different (ab) then

scallops are different as well

Identical offset (a=b) have same scallops

The corner downlight are @ 45o

The alignment of scallops with architectural lines

The lighting planner or lighting designer should understand the architectural space, if there is any


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lines , groves in the vertical then the lighting should be aligned to achieve good result, otherwise

lighting could make scallops that not in line with architectural vertical lines

The scallops are not aligned with

architectural vertical lines

The scallops are aligned with






The scallops are not aligned with architectural vertical lines

Intensity of lighting scallops The intensity of lighting scallops should not be high , using computer software like I could help the


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designer to make the right choice for the design.

Soft scallops Strong scallops

LED Downlight with scallops LED is an efficient lamp source that is expected to replace all conventional lamp sources soon,

however there are very different quality of LED ranging from very poor to excellent LED when it

comes to scallop shape and color, so it is strongly advisable to check the downlight in a real

physical mock.

One of the criteria is how different in color are the LEDs (the different of white light from one LED

to another) which called MacAdam ellipse or SDCM (Standard Deviation Color Matching)

The products used for the next guide from ERCO has less than 2 SDCM which means no color

visible to human eye.

4 Step MacAdam ellipse or

SDCM is visible to human eye

2- step MacAdam ellipse

(SDCM) are not visible

`


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The bad quality of scallop shape and the

difference in color make LED very poor

in architecture.

A lot of difference in color SDCM >4 SDCM <2

Vertical Planner Guide for Grazing and Scalloping effect

In the following rendering I used some ERCO luminaire with different beam angle to show the

different effects, all lamp source were LED and to ensure right planning I made real mock up to see

the difference between the scallop rendered by I evo and the physical mock. The results of I evo

were very accurate and ERCO photometrics were very precise as well.

Unfortunately not all manufacturer provide precise photometric, so I strongly recommend to use

well know manufacture for accurate photometrics and ideally should be tested in mock-up to

achieve good results.


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Physical mock up @ ERCO Mock Room

Dubai Office (LED <2 SDCM)

Rendered Image using the same ERCO

ULD photometric in I evo

In the following guides which is called Vertical Illuminance Guide (VIG) I used offset and spacing as

follows:

All offset are from center of luminaire to wall

All spacing are between center of luminaires

VIG-1 VIG-2

Beam Narrow Spot 5o

Offset 150 mm

Beam Spot 15o

Offset 250 mm



Spacing 500 mm

Luminaire ERCO 87629

Spacing 700 mm


VIG-3 VIG-4

Beam Food 27o

Offset 300 mm

Spacing 1000 mm


Beam Wide Flood 50o

Offset 400 mm

Spacing 1000 mm


VIG-5 VIG-6

Beam 5o and 27o Beam 5o and 47o



Offset 150 mm

Spacing 500 mm


ERCO 87639 (Dimmed to

15%)

Offset 150 mm

Spacing 750 mm


ERCO 40014 (Dimmed to

10%)

Uniform grazing light Uniform Grazing is used to avoid the scalloping effect of light on wall and could be done perfectly

with LED liner luminaire like ERCO Lightgap Luminaire.

The luminaire in a cove of architecture in a continuous row.

Uniform Grazing is perfect light for Textured wall.

Uniform wallwashing Wallwashing is a technique that is makes the lighting design for a wall free from any bad scallops

and enhance architectural, as a matter of fact I prefer this solution and find it much better than

grazing light with scalloping effects simply because it shows wall clean and provide a sort of

indirect lighting.

Uniform wallwashing enhance architectural and provide clean modern Appearance



LED recommended be less than 2 SDCM to achieve similar effect

Wall washer is a luminaire used for wallwashing, it has to be tested

by visual mock up or by using photometric in lighting software to

ensure uniform wallwashing.

It would be very good to consider LED with SDCM<2 since

wallwashing with visible difference in color would not be good for

the appearance.

For spacing and offset you should check manufacture recommendation. however the role of thumb

is The offset of a wallwasher is 1/3 of the wall height

The spacing of luminaire is equal to offset.

For 3 meter height the offset = 1 meter and spacing =1 meter.

The corner wallwasher should have equal offset from both wall to avoid strong lighting on the other

side wall.

VIG-7 Wallwasher offset is correct for the facing

wall but for the side wall which make

unpleasant high contrast.

Offset ideally form both wall, using computer

software help avoiding such high contrast.

Beam Wallwash

Offset 1000 mm

Spacing 1000 mm




Accent lighting for abject on wall Accent lighting is a very important and could be very attractive if done properly. It highlights an

object and makes it an eye catcher ,

But many people fail to make it right because not having the right offset for a spotlight to highlight

a painting on wall.

Close offset is common mistake which makes too strong lighting above the painting which makes it

difficult to see the painting details instead of highlighting the painting

Close offset is common

mistake

Proper offset makes the

painting looks

Attractive.

To achieve a good accent light on painting, the spotlight has to have an offset from wall so that the

center of the light is tilted by 30o to the center of the painting.

The following charts shows the proper offset from center of spotlight to wall for different ceiling

hight.



For 3 meter ceiling height, the offset of spotlight

is 850 mm from wall.

The beam angel of spotlight should be selected so that the beam light cover the painting , beam of light

shouldn’t be too small or too big for the painting size

The closest beam angle to the painting size should be selected

The VAG (Vertical Accent Guide), in the following guides for accent lighting, you can see different beam

and different sizes of paintings for a ceiling height of 3 meter



VAG-1 VAG-1

Beam Narrow Spot 5o

Offset 850 mm

Tilt of spotlight 300

Object Size 500mm x300mm

Beam Spot 15o

Offset 850 mm



VAG-3 VAG-4

Beam flood 28o

Offset 850 mm



Beam Wide flood 50o

Offset 850 mm





VAG-5 VAG-6

Beam Oval flood 15ox60o

Offset 850 mm


Object Size 2000 mm x600 mm

Beam Oval flood 15ox60o

Offset 850 mm


Object Size 800 mm x2000 mm

The narrow side facing the wall The wide side facing the wall

VAG-5 and VAG-6 is using the same beam angle which is oval flood 15ox60o , however in VAG-5

the narrow side was facing the wall while in VAG-6 the wide side was facing the wall .

VAG-6 could be used form more than one paintings

with the same dimension, like in the example it was

used for three painting please in a row of around 2

meter

Lumen and Center beam of Spotlights In order to make the painting attractive it should have more light by at least 5 times than the

surrounding, this could be achieved by selecting the proper lumen of spotlight and also the center

beam intensity of spotlight, using computer software ensure proper selecting of spotlight bean angle

and intensity to make the object as an eye catcher.



Using computer software like

DIALux evo help ensuing the

proper selection of lumen and

center beam of spotlights.

You can see the other lighting guides on the following link

https://ezzatbaroudi.wordpress.com/

ldg-2 · rendering made by dialux evo square downlight with trapezoid beam (right) round downlight...

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