2. INTRODUCTION
Essential for efficient vision
Imperfect light cause ill health
Imperfect light damage the eyesight and produce physical and mental
discomfort
Visible light has wave length of electromagnetic waves from 380nm to
760nm
3. MEASUREMENT OF LIGHT
Measurement of lighting includes the foot-candle and lumen type. The four
measurements of lights are as follows:
Luminous intensity or power of artificial light is measured by the standard
“Candle”
Amount of light given off by burning wax candle is 120grains/hour is
called candle power
Illumination received from 1 candle at a distance of 30.48 cm known as
10.76 lux
The illumination is measured by instrument called photometer. The light is
measured by other parameter such as:
Luminous flux(flow of light)expressed in lumens
Illumination(amount of light reaching a surface)
Luminance( brightness i.e., amount of light reflected from a surface)
4. ESSENTIAL OF GOOD LIGHTING
Sufficiency and uniformity in distribution
Absence of Glare
Sharp shadow is disturbing and also it should not be patchy , as it can lead
to accident
Over bright Light
5. SOURCES OF LIGHT
NATURAL
• Sun
ARTIFICIAL
•Lasers Electric Welding
•Carbon Arc
•Tungsten filament lamps
•Fluorescent lamps
6. NATURAL LIGHT
It is obtained not only from sky but also from reflection
It depends on time of day , season, weather and Atmospheric pollution
It is better and cheaper than Artificial light
It depends upon design , orientation , location , type and size of house
North and south facing house gives uniform illumination and white
washing gives good light
MINIMUM AREA FOR WINDOWS OR DOORS
Living and bedrooms:1/10 of the total room area
School room:1/5 of the total room area
Factory : 1/5 of total room area
Cow shed:1/5 of total room area
7. ARTIFICIAL LIGHT
Best form of artificial lighting is electric tube light
Gas lighting either coal gas or acetylene , or petrol gas is liable to pollute
air with carbon monoxide
Living room: 75.35 lux
Stairs : 21.5 -43.05 lux
Class & library room: 107.64 lux
Hotel : 64.58 lux
Office general: 107.64 lux
Hospital ward : 32.29 lux
Industrial processes: 59.20 lux
Operation theater: 1076.39 lux
8. FACTORS AFFECTING GOOD LIGHTING
Sufficiency ( Illumination OF 161.45- 215.27 Lux)
Distribution( uniform Light with same intensity)
Absence of Glare
Absence of Sharp Shadows( Slight shadows are inevitable, sharp
contrasting shadows are disturbing)
Steadiness ( Constant source of light without flickering)
Color of Light ( Artificial light has to approximate with day light color)
Surroundings ( Ceilings and roof should have a reflection factor of 80%,
contrasting colors to prevent accidents in culverts , bridges)
9. UNITS OF LIGHT
LUMINOUS INTENSITY : It is the power of a light source considered as
a point radiating in all directions, measured as Candelas
LUMINOUS FLUX: It is the flow of light related to unit of solid angle
measured in Lumens
ILLUMINANCE: It is the amount of light reaching a surface measure in
lux /unit area
LUMINANACE: It is the amount of light reflected from a surface
measured in Lamberts
10. Measurement of Light with UNITS
Luminous Intensity
(CANDELA)
Luminous Flow
(LUMEN)
Illumination
(LUX)
Luminance
(LAMBERT)
11. METHODS OF IMPROVE LIGHTING
1. NATURAL ILLUMINATION
a) Natural lighting
Building faced north and South will ensure uniform light at morning to
evening
tall narrow window gives greater penetration of light and a broad window
gives greater diffusion of light
Interior of room with white ceiling , with upper portion of walls to be light
colored, lower portion dark tint
Proper interior, design and orientation of building: placement of windows,
skylight reflection and penetration and doorways.
12. Orientation: brightness of sky is not constant on east & west and therefore
the illumination is subject to variation in building east or west.
Removal of Obstruction : whole or partial removal of obstruction is the
most effective single improvement in lighting
Windows : Tall window ensure greater diffusion of light. Window area is
correlated to the purpose the room is intended to serve . It also penetrate
more light in rooms, but broader windows diffuse more light.
Interior of the Rooms : Day light illumination is liable to change from
moment to moment; its not measured in terms of foot candles. Re-liance is
placed on a factor called daylight factor.(DF)
DF = Instantaneous illumination indoors X 100
Simultaneously occurring illumination outdoors
13. Advantages of having natural light:
Reduces bilirubin level in case of premature infants having
hyperbilirubinemia
Maintains the biological rhythm of body
Stimulates melanin synthesis
Activate the precursors of Vitamin D
Maintain the adrenocortical Secretion.
14. 2. ARTIFICIAL ILLUMINATION
Artificial Lighting:
Artificial light can be produced by using tungsten filaments , lamps or
fluorescent lamps . Even lasers and electric weldings or carbon can
produce artificial light.
Depending on the type of projection of light towards working area, or
upwards or downward and of reflection basis, it is divided into 5 types:
Direct Lighting
Semi - direct Lighting
Indirect Lighting
Semi - indirect Lighting
Direct & Indirect lighting
15. Electric light is the method of providing artificial illumination . The
different types of electric lights are:
Filament Lamps
Fluorescent Lamps
Emission of energy by Lamps:
Lamps Light(%) Heat(%)
Filament 5 95
Fluorescent 21 79
16. Different types of Fluorescent lamps are:
Neon-filled sodium discharge lamp
Mercury vapor lamp
Cold cathode neon lamp
Shadowless light
Other sources of artificial light are:
1. Gas light
2. Gas burner
17. STANDARDS OF LIGHTING
Eye responds to a range of illumination ranging from 0.1(full moon light )
to 100000 lux (bright sunshine)
The illumination level should be 30 times higher than the level at which
the task can just be done.
For practical situations and various activities, the following values have
suggested by the illuminating engineering society:
Visual task :Illumination
Casual Reading:100
General office work: 400
Fine Assembly:900
Very severe task:1300-2000
Watch making: 2000-3000
18. CRITERIA FOR GOOD
LIGHTING
1.Proper Illumination
For satisfactory vision Minimum requirement of 161.45 -215.27 lux is
required
Stairs:53.81 lux
Corridors:1076.39 lux
2. Uniform distribution
Light Fall over the whole or the area of work with same intensity.
3. Not too bright light
Bright light cause constriction of pupils & more strain to eye where as with
glare light one will be unable to visualize the object.
4. Absence of flickering
It creates eye strain
19. 5. No sharp or contrast shadows:
It cause confusion and should not be present in field of vision
6. Too bright light
It injure the eye through photochemical reaction in retina, blue light injury
may occur with sustained exposure exceeding 0.1mW/cm2 and retina may
burn with prolonged exposure to 10W/cm2.
7. Too light illumination:
Eye strain and seasonal affective disorders
8.Thermal effects of light:
Too much heat cause injury to iris , lens, cornea & skin due to exposure to
laser radiation
21. PREVENTION OF EFFECTS OF POOR LIGHTING
Proper illumination
Appropriate training
Proper design of buildings
Proper design of equipments
Protective eye shield
Not to look to the source of light
Avoid looking directly to high intensity sources such as laser or Carbon arc
Proper planning of town