Chapter 6 Directional Effects of Lighting 1

© 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 6 Directional Effects of Lighting © 2006 Fairchild Publications, Inc. 3 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

© 2006 Fairchild Publications, Inc. 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 10 central field of vision

Visual Comfort

…increase the visible surface area of the source

…redirect the light straight down

…block light with a baffle

Chapter 6 Directional Effects of Lighting © 2006 Fairchild Publications, Inc. 18 Lamp choice R, PAR and MR lamps Non-specular reflectors, baffles

Chapter 6 Directional Effects of Lighting © 2006 Fairchild Publications, Inc. 19 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

Chapter 6 Directional Effects of Lighting © 2006 Fairchild Publications, Inc. 20 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

23 Illumination Zones: task oriented –Immediate task –Area surrounding the task –Background zone 3 zone 1zone 2

Chapter 6 Directional Effects of Lighting © 2006 Fairchild Publications, Inc. 24 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

Chapter 6 Directional Effects of Lighting © 2006 Fairchild Publications, Inc. 26 Incident and Reflectance Angle of incident and reflectance angle of incident angle of reflection

Chapter 6 Directional Effects of Lighting © 2006 Fairchild Publications, Inc. 27 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%

Chapter 6 Directional Effects of Lighting © 2006 Fairchild Publications, Inc. 29 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

Chapter 6 Directional Effects of Lighting © 2006 Fairchild Publications, Inc. 30 Controlling Light Reflection in luminaires: –Shiny aluminum on inside surfaces –Reflector contours: Spherical Parabolas Ellipses

Chapter 6 Directional Effects of Lighting © 2006 Fairchild Publications, Inc. 31 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

Chapter 6 Directional Effects of Lighting © 2006 Fairchild Publications, Inc. 32 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

Chapter 6 Directional Effects of Lighting © 2006 Fairchild Publications, Inc. 40 Translucent materials Glass and other non-opaque materials –Transparent –Semi-opaque –Fritted or frosted –Internal materials –Colors

3-form

Architecture

Elements

Chapter 6 Directional Effects of Lighting © 2006 Fairchild Publications, Inc. 44 Patterns of Light Objects appear attractive by positioning a light source to the side at 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