chapter 6 directional effects of lighting 1. © 2006 fairchild publications, inc. directional...

Chapter 6

Directional Effects of Lighting

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© 2006 Fairchild Publications, Inc.

Directional Effects

• Intensity and direction– An object’s appearance– Architectural features– Ability to perform a task– Quantity of illumination

• Layered lighting plans

Chapter 6Directional Effects of Lighting


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Brightness and Glare

• At source of light• At destination of light• From different angles

Controlling Brightness– Subjective responses– Context of the situation– Personal vision attributes– Light sources– Directional qualities– Simultaneous contrast – Characteristics of elements of the

design

Glare

• Contrast between two areas is severe (greater than 3:1)

• Glare can cause:– A loss in visual acuity– Eye fatigue and strain

Glare-ing situations

• Settings that require contrast for effective visibility and attention

• Task lighting

Direct Glare

• Examples:– Sunlight – Unshielded incandescent lamp greater

than 25 watts– Unshielded downlights– Variation in lighting level in adjacent

spaces

Indirect Glare– Light source reflected from a light color

or a shiny surface– Specular materials (called veiling

reflections):• Glass• Mirrors• VDT screens• High-gloss surfaces, such as a highly

polished wood


Controlling Glare

– Locate luminaires out of field-of-vision– Use lower-brightness luminaires (linear

source, not point source)– Choose smaller apertures– Shield light source with baffles and

lenses

Eye’s Field of Vision

• Central field of vision:– ~2 degrees above and below the direct line of sight – Visual acuity (ability to see detail) is best in this

range

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central field of vision

Visual Comfort

…increase the visible surface area of the source

…redirect the light straight down

…block light with a baffle



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Lamp choice

• R, PAR and MR lamps• Non-specular reflectors, baffles



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Controlling Light • Refraction:

– Example: Light passing through a prism• Direction of a light source altered to

maximize amount of light falling on a surface:– Example: Prismatic lenses from glass or plastic.

Prisms refract light to the space and reduce glare

• Glass and plastic lenses without prisms distribute illumination through diffusion or transmission



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Controlling Light• Transmission:

– Allows incident light to pass through• Direct:

– Majority of light passes through material • Mixed:

– Most light passes through in a semi-scattered matter

• Diffused:– Light scattered in many directions

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Illumination Zones: task oriented

– Immediate task– Area

surrounding the task

– Background

zone 3

zone 1zone 2



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Reflectance and Texture

• Specular reflection: Results when incident light is reflected

• Semi-specular reflection (etched glass): Most of the incident light is reflected

• Diffused reflection: Incident light scattered in a variety of angles

Reflectance• The ratio of incident lighting to the

light reflected from a surface or material

• Expressed as a percentage• Environmental factors that affect

reflectance values in a space:– Size of the room – Location of a surface– Light sources

© 2006 Fairchild Publications, Inc. 26Chapter 6Directional Effects of Lighting

Incident and Reflectance

• Angle of incident and reflectance

angle of incident

angle of reflection



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Reflectance Effects of Texture

• Light is reflected or absorbed: – Smooth and shiny materials reflect more light

than rough and heavily textured materials• Specular reflection: Results when

incident light is reflected• Semi-specular reflection (etched glass):

Most of the incident light is reflected • Diffused reflection: Incident light

scattered in a variety of angles

Lighting Conditions

100%

30% 30%



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Controlling Light• Some lamps designed for optical control: – R, PAR and MR lamps

• Elements of luminaires designed to control illumination:– Shielding devices– Reflection– Refraction– Diffusion



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Controlling Light

• Reflection in luminaires: – Shiny aluminum on inside surfaces– Reflector contours:

• Spherical• Parabolas• Ellipses



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Controlling Light and Accent Lighting

• Patterns of light and shadow can reinforce elements of interior architecture and objects of emphasis

• Required for accent lighting:– Select what should be highlighted– Select which objects or areas should be

hidden by shade and shadow



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Patterns of Light Shade and Shadow • Shape and length of shadows

dependent upon:– Intensity of a light source– Angle of direction– Distance from object

• High intensity/close to object:– Dark shadow with defined details

• Light sources at a low angle:– Elongated shadows

Lighting Objects

Two-dimensional objects



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Translucent materials

• Glass and other non-opaque materials– Transparent– Semi-opaque– Fritted or frosted– Internal materials– Colors

3-form

Architecture

Elements



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Patterns of Light• Objects appear attractive by positioning a light source to the side at 15-45 degrees

• Shiny materials: Light source at side of object

• Glass objects: Illuminated from above and below

• Pinhole opening < 30 degrees angle of beam enhances form, textures, and shapes

Luminaires

chapter 6 directional effects of lighting 1. © 2006 fairchild publications, inc. directional...

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