CHAPTER 3

BASICS ON LIGHTING

                         In this session we are going to light up the room. It consists of selecting and positioning the desired light that we want to install. Before getting started it is better to understand the basics of lighting and the terms used in it .

BASICS OF INDOOR LIGHTING
                         A room may have multiple functions: a place in which to relax, to work on the computer, to do arts and crafts, to cook, or share meals with friends and family. This is why lighting features need to correspond to the setting or application of each room. “The best advice I can offer is the following: no matter what you do, or what you hope to accomplish, always install three types of lighting in a room,” says Patricia Rizzo, of the Lighting Research Center . Too often, people expect a single light source to fill all their needs. And yet, each one of the three types of lighting fills a specific need: Ambient, Task and Accent Lighting.

AMBIENT LIGHTING
                       The purpose of overall, or ambient, lighting is to light up an entire room so that people are able to easily and safely move throughout the space. Light ‘bounces’ off the walls to lighten as much space as possible.
Eg : Track light , Ceiling mounted fixture, Wall-mounted fixture, down-light, Floor lamp, Table lamp etc.

TASK LIGHTING
                       Task lighting sheds light on the tasks that a person carries out in a given space such as reading, writing, computer work, where a brighter light is required in a smaller focal point of the room. For more congenial lighting, it is often best to avoid harsh lights or lighting that casts troublesome shades. It is also quite practical to install a single switch for focal lighting, independent from the room’s overall lighting switch.
Eg : Pendant lighting, Portable or desk lamp etc.

ACCENT LIGHTING
                        Accent lighting is used mainly to focus on a specific point of interest or to achieve a desired effect. This type of lighting gives the impression of a larger space; it is more frequently used to highlight an architectural feature, a plant, a sculpture or a collection of objects. As a general rule of thumb, effective ambient lighting requires the installation of three times more light on the focal point than existing light on the rest of the space.
Eg : Track light, Directional recessed fixture or downlight, Wall-mounted fixtures etc.

TERMS USED IN LIGHTING

Luminous flux (lumen = lm)
                         This is the total light output of a light source (lamp).The luminous flux is of particular importance, because it is the quantity that is used to describe the "brightness" of a light source. For example, a 100 watt filament lamp would produce about 1,360 lumen. A 30 watt fluorescent lamp would produce about 1,600 lumen. The luminous flux is therefore the light output by the lamp.
Luminous intensity I (candela = cd)
                         Luminous intensity is the light flux of a lamp or light bulb emitted in a specific direction. The type of reflector of a lamp or luminaire determines the light intensity distribution and is frequently shown as a light intensity distribution curve.
Illumination E (lux = lx = lm/m²)
                        Illumination is divided by the light flux of a lamp into lumen, where one lux is an illumination of one lumen per square metre. The light of a full moon would provide an illumination of about 1 lux, good workplace lighting about 1,000 lux, and on a sunny day outdoors, the illumination intensity would be about 100,000 lux.

Luminance L (cd/m²)
                               Luminance is a measure of the brightness of an illuminated surface. In addition to the luminous intensity, the reflection factor of the surface is also decisive.
Luminous efficiency
                               The luminous efficiency (Lumen per watt) is a measure of the efficiency of lamps. The more light (lumen) obtained for the amount of power (watt) input, the less the costs (Euro) are and the better the economy. Whilst tungsten-halogen lamps provide about lumen per watt, this can about 75 lumen per watt with fluorescent lamps.
Luminous color and color temperature
                               The luminous color of a light source is described by the color temperature. With filament lamps this is about 2,700 Kelvin (K) and with fluorescent lamps this is above 6,000 K. A light source with 3,000 K has a larger proportion of red, a light source with 6,000 K has a larger proportion of blue.
Colour rendering
                               Color Rendering Index (CRI) is a scale from 0 to 100 percent indicating how accurate a "given" light source is at rendering color when compared to a "reference" light source. The higher the CRI, the better the color rendering ability. Light sources with a CRI of 85 to 90 are considered good at color rendering.