BASICS OF LIGHTING DESIGN:

1)     ILLUMINANCE: Amount of light falling on a surface is called illuminance. The purpose of all lighting is to produce illumination.

2)    LUMINANCE: luminance is the amount of light that leaves a surface, either by transmission through the material or, more commonly, reflection from the surface.

(In above example, light is falling on a board and is being reflected)

3)     LUMENS: The most common measure of light output (or luminous flux) is the lumen. Light sources are labeled with an output rating in lumens. For example, a T12 40-watt fluorescent lamp may have a rating of 3050 lumens. A measurement of light emitted by a lamp. As reference, a 100-watt incandescent lamp emits about 1600 lumens.

4)     LIGHT OUTPUT: Quantity of light emitted per second in a particular direction.

 5)  COLOUR TEMPERATURE: The color of the light source. By convention, yellow-red colors (like the flames of a fire) are considered warm, and blue-green colors (like light from an overcast sky) are considered cool. Color temperature is measured in Kelvin (K) temperature.

6)     COLOR RENDITION: How colors appear when illuminated by a light source. Color rendition is generally considered to be a more important lighting quality than color temperature. Most objects are not a single color, but a combination of many colors

7)     GLARE: The excessive brightness from a direct light source that makes it difficult to see what one wishes to see. Bright lights reflecting off a television or computer screen or even a printed page produces glare. A bright object alone does not necessarily cause glare, but a bright object in front of a dark background, however, usually will cause glare

SELECTING LIGHTING EQUIPMENTS:

There is a wide range of lamps, luminaires and controls available to the designer

1)     COMPARISON BETWEEN LED AND CFL (energy savers);

·        To understand LED light benefits, it’s important to understand the difference between the two bulbs. LED light bulbs produce light when an electrical current passes through them. LED transfers current through a semi-conductor. This movement of electrons generates light. In CFL bulbs an electric current flows between electrodes at each end of a gas-filled tube. The reaction creates ultraviolet light and heat, which is then changed into light when it hits a phosphor coating on the bulb’s interior. This process takes anywhere from 30 seconds to 3 minutes to complete,, which is why it can seem as if your CFL light takes a while to be fully lit.

·        LEDs emit very little heat. In contrast, incandescent bulbs release 90% of their energy as heat, CFLs release about 80% of their energy as heat

·        LEDs apart from incandescent bulbs and CFLs have long life. LED light bulbs can last anywhere from 20,000 to 50,000 hours, or up to five times longer than any comparable bulb on the market.

·        Cost of LED bulbs is more than CFL

THE DIFFERENCE BETWEEN LUMENS AND WATTS

Something else consumers need to understand while analyzing CFL vs LED bulbs is the difference between lumens and watts. Consumers are used to buying light bulbs based on watts, or how much energy they consume. It didn’t matter how much light (lumens) they provided. Now, as a way to differentiate LED vs CFL bulbs, manufacturers are classifying the new energy-efficient bulbs by their lumens. You are buying your bulb based on the amount of light you want rather than the energy used by the bulb.

Admittedly, it can be confusing. Here’s the basic point to keep in mind: More lumens equals more brightness. But exactly how many lumens is equivalent to what was once, say, a 60-watt bulb? Here’s a breakdown to give you the basic new LED vs CFL light bulb math:

• To replace a 100-watt incandescent bulb, choose a bulb with about 1600 lumens.
• To replace a 75W bulb, choose a bulb with about 1100 lumens.
• To replace a 60W bulb, choose a bulb with about 800 lumens.
• To replace a 40W bulb, choose a bulb with about 450 lumens.

2)     COMPARISON BETWEEN LED AND HID’s:

·        HID stands for high intensity discharge. It is often referred to as a xenon light, referencing the gas that the bulb contains. It differs to both halogen and LEDs in that the source of its light is an electric arc that takes place between two tungsten electrodes. In a similar fashion to LEDs, HID headlights offer brighter light than halogens, at a higher level of efficiency. This is the main reason for their use in headlights

·        From a brightness perspective, HIDs are king. LEDs do very well, and some can achieve HID levels of illumination, but in a standard comparison the HID will win. 

·        Due to the nature of HIDs, they have a brief warm-up period, in the order of 5 seconds. During this time, you don’t have the brightest light. LEDs on the other hand have an instant on ability, so you go immediately from darkness to full brightness.

·        HIDs produce light in the infra-red (IR) spectrum along with visible light. This is beneficial for people in colder climates as it assists in melting snow and ice, which may otherwise block up headlights. LEDs do not emit IR light

·        In this matchup, LEDs come out the winner in four major areas: efficiency, lifespan, durability, and low maintenance. However, there are still some instances where an HID is still a smart choice. For example, HIDs make sense for temporary low cost lighting, extreme high temperature applications

3)     COMPARISON BETWEEN LED AND INCANDESCENT BULB:

·        LEDs are very efficient relative to every lighting type on the market and extremely efficient relative to incandescent bulbs. Typical source efficiency ranges 37 and 120 lumens/watt. Incandescent lights are the worst of all the modern lights in terms of efficiency because so much of the energy (90%) goes towards generating heat instead of light. Their source efficiency (the amount of light emitted from the bulb in general) is around 10 lumens/watt 

·        LEDs last longer than any light source commercially available on the market. Lifespans are variable but typical values range from 25,000 hours to 200,000 hours or more before a lamp or fixture requires replacement. Incandescent lights have lifespan of (roughly 1,200 hours).

·        LED lighting has relatively high initial costs and low lifetime costs. The technology pays the investor back over time (the payback period). The major payback comes primarily from reduced maintenance costs over time Incandescent lights are by far the cheapest light to purchase on the market but they are a bear to maintain over time because their lifespan is so short. 

·        LEDs have virtually no warm-up time. They reach maximum brightness near instantaneously. Incandescent lights don’t generally require a warm-up time but there can be a short delay as the filament heats up when operating at extremely cold temperatures.

Use This Sheet for collecting information about the room that is to be lit and its lighting requirement (COURTESY CIBSE GUIDELINES)

DIRECT VS INDIRECT LIGHTING:

Direct light means that there is nothing between the light source and the area that is subjected to light. If the area is not receiving direct lighting, but is still illuminated to a certain degree, this means that this area is receiving indirect light. A good example is the difference between a person that is tanning under the sun, and a person under an umbrella. The person under the umbrella is still visible, because of indirect light reflecting from the sand and other surfaces.

Direct lights are ideal for areas where we perform tasks, as well as for dining areas. Kitchens and bathrooms are perhaps where we need the most direct light. Light bouncing off a wall and door in one room provides indirect light for a hallway provides indirect lighting for the room

Natural light from a window may also offer indirect light as you sit away from the window, out of its view. Direct light is much like a beam shining on a specific area, while indirect light is the ambient lighting still evident outside that beam.

RECOMMENDED LUX LEVELS IN HOME:

1)     Living room   200 lux

2)     Dining room  250 lux

3)     Kitchen          250 lux

4)     Bedroom        180 lux

5)     Bathroom        150 lux