Light and Lighting

Introductiono Good lighting can make or break a home in the same way that

furnishings and interior decoration set a style, yet too often lighting is treated as an afterthought.

o Designing light require the architect to start with the space to light and most importantly will look at what space is FOR.

o Designers must treat space as a dynamic entity because homes are not static showpieces, people live in them and lighting design must account the different activities in each spaces.

o Every human activity needs different lighting state that gives the right levels of light for visual task on appropriate mood.

o Finally, the quality of lighting design must evoke the emotional feeling of the space.

Light

oEnergy producing brightness: the energy producing a sensation of brightness that makes seeing possible

o Is visually perceived radiant energy on the electromagnetic spectrum in the range visible to the human eye.

o Visible light comprises only a very small part of the energy spectrum yet makes it possible for people to see.

o Light and color affects human sight. o Color is determined by wave length

(370 nanometers to 800 nanometers)1 nanometer = 1billionth of a meter

o Longest wavelength has lowest frequency and shortest wavelength has highest frequency

Fundamental Laws of Light

Electromagnetic Spectrum

Sources of LightIncandescence o In an incandescent light source, hot atoms

collide with one another. These collisions transfer energy to some electrons, boosting them into higher energy levels. As the electrons release this energy, they emit photons. Some collisions are weak and some are strong, so the electrons are excited to different energy levels and photons of different energies are emitted.

o Candle light is incandescent and results from the excited atoms of soot in the hot flame. Light from an incandescent light bulb comes from excited atoms in a thin wire called a filament that is heated by passing an electric current through it.

Sources of LightLuminescence

o A luminescent light source absorbs energy in some form other than heat, and is therefore usually cooler than an incandescent source. The color of a luminescent source is not related to its temperature. A fluorescent light is a type of luminescent source that makes use of chemical compounds called phosphors..

Sources of LightLasero A laser is a special kind of light source that

produces very regular waves that permit the light to be very tightly focused. Laser is actually an acronym for Light Amplification by Stimulated Emission of Radiation. Each radiating charge in a non laser light source produces a light wave that may be a little different from the waves produced by the other charges. Laser sources have atoms whose electrons radiate all in step, or synchronously. As a result, the electrons produce light that is polarized, monochromatic, and coherent, which means that its waves remain in step, with their peaks and troughs coinciding, over long distances.

Behavior of Light

o Light behavior can be divided into two categories: how light interacts with matter and how light travels, or propagates through space or through transparent materials. The propagation of light has much in common with the propagation of other kinds of waves, including sound waves and water waves.

o is the bending of light when it passes from one kind of material into another. Because light travels at a different speed in different materials, it must change speeds at the boundary between two materials. If a beam of light hits this boundary at an angle, then light on the side of the beam that hits first will be forced to slow down or speed up before light on the other side hits the new material. This makes the beam bend, or refract, at the boundary.

Refraction

Reflectiono Reflection also occurs when light hits the

boundary between two materials. Some of the light hitting the boundary will be reflected into the first material. If light strikes the boundary at an angle, the light is reflected at the same angle. Light that is reflected from a flat boundary, such as the boundary between air and a smooth lake, will form a mirror image. Light reflected from a curved surface may be focused into a point, a line, or onto an area, depending on the curvature of the surface.

Types of Reflectiono Specular – Directed from a smooth

polished surfaceo Diffused – A scattered reflection of

light from an irregular surface or an erratic dispersion through a translucent material.

o Reflectance – The ratio of the radiation reflected by a surface to the total incident on the surface

o Absorptance – The ratio of the radiation absorbed by a surface to the total incident on the surface

o Transmittance – The ratio of the radiation transmitted through and emerging from a body to the total incident on it, equivalent to 1 minus the absorption

Materials in relation to Light

o Opaque – Impenetrable to lighto Translucent – Transmitting and

diffusing light so that bodies on the opposite side are not clearly visible

o Transparent – Capable of transmitting light so that bodies situated beyond or behind can be distinctly seen.

Lighting

The science, theory, or method of providing illumination through the use electric lamps

Lighting Fundamentalso Candlepower – The Intensity of light

from a source in a certain direction, and measured in candelas.

o Coefficient of Utilization – The ratio of illuminance to the lumens radiated from the light source.

o Efficacy – The ratio of the approximate initial lumens produced by a light source divided by the necessary power to produce them.

Lighting Fundamentals o Footcandle – A unit of illuminance

measurement; the number of lumens that are incident on each square foot of work surface. 1fc = 10.76 lux

o Illuminance – The light falling on a surface, measured in footcandles or lux.

o Lumen – A measure of total light producing output of a source; the quantity of visible light emitted.

Lighting Fundamentalso Luminaire – An assembly used to house

one or more light sources. Also called lighting fixture.

o Luminance – The emitted or reflected light from a surface in a particular direction, measured in candelas per square meter.

o Lux – A unit of measurement used to gauge the illuminance falling on a surface; the number of lumens incident on each square meter

Luminance and Illuminance

Categories of Luminaireso Direct: 90 – 100% downwardo Semi direct: 60 – 90% downwardo General diffuse: 40 – 60% both

downward and upwardo Direct – indirect: little light is emitted in

the horizontal planeo Semi – indirect: providing 60 – 90% of

its output upwardo Indirect: providing 90-100% of its

luminous output upward.

Classification of Luminaires

o Recessedo Ceiling Mountedo Track Mountedo Wall mountedo Suspendedo Architectural o Portableo Pole Mountedo Bollardo Outdoor

Lighting and VisionFactors that affect visual performance independent of lighting

o Contrast: refers to the luminance difference between the critical detail of a task and its immediate background

o Size: refers to the size of the visual tasko Time: refers to the time a visual task is

presented.

Factors that affect visual performance dependent on lighting

o Task Luminanceo Reflectance of a surfaceo Veiling Reflections: reflections that

create a luminous veil over a visual task

o Glare: an annoying or painful sensation caused by the non-uniformity of lighting

Lighting and Vision (cont.)

Glare

Veiling Reflection

The following means can reduce discomfort glare

oDecrease the luminance of the offending source of light

oReducing the area or size of the offending source

o Increasing the luminance of surfaces surrounding the offending source

Lighting and PsychologyResearch has resulted in some approaches to lighting a space that tend to reinforce some subjective impressions.

o Visual Clarity: reinforced by bright, uniform lighting combined with high brightness of the walls

o Spaciousness: reinforced by uniform wall lightingo Relaxation: reinforced by non-uniform lighting and

lower ceiling brightnesso Privacy/Intimacy: reinforced by non-uniform

lighting (low levels around the occupants, higher levels further away)

o Pleasantness/preference: reinforced by non-uniform lighting with high wall brightness

Artificial Light Sourceso Incandescent Lamps

o Fluorescent Lampso High – Intensity Discharge Lamps

o Mercury Lampso Metal Halide Lamps

o High Pressure Sodium Lampso Low Pressure Sodium Lamps

o Electrodeless Lampso Compact arc xenon and Mercury Lamps

o Electroluminescent Lampso Light Emitting Diodes

o Carbon arc Lampso Gaslights

Lighting Calculationso IlluminanceInverse Square Cosine Law

E =(I cosx)/D2

Where: I is the Luminous Intensity in CandelasD is the distance between the source and the pointand the angle x between the normal or

perpendicular to surface A and the direction along the distance D

o LuminanceL = rE/

Where: r is the reflectance, and E is the illuminance in lux

Types of Lightingo General Lighting

Types of Lightingo Accent Lighting

Types of Lightingo Decorative Lighting

Types of Lightingo Task Lighting

Types of Lightingo Kinetic Lighting