A KIND OF LIGHT POLLUTION WHICH EMITS FROM A LIGHT SOURCE

1. BY, SUSHILKUMAR
T. Y. B. ARCH 13 SEM:5
PIHCA

2. UNITS (LATIN)
• Candela (CANDLE) : the SI unit of luminous intensity. One candela is
the luminous intensity, in a given direction, of a source that emits
monochromatic radiation of frequency 540 × 1012 hz and that has a
radiant intensity in that direction of 1/683 watt per steradian.
• Lux (light): the si unit of illuminance, equal to one lumen per square
metre.
• Lumen {light} : the si unit of luminous flux, equal to the amount of light
emitted per second in a unit solid angle of one steradian from a
uniform source of one candela.

3. LIGHT TRESPASS
• Light trespass is an environmental impact.
• It is a non useful light which causes light pollution.
• Unwanted light which causes annoyance, discomfort, distraction, or a
reduction in
• Visibility.
• Generally caused by poor lighting design or inadequate optical control
in the fixtures.
• Light trespass (obtrusive lighting) is defined by three major
interrelated elements.
• The three elements are:
1. Spill light
2. Glare
3. Sky glow

4. SPILL LIGHTING, GLARE AND SKY GLOW

5. GLARE
• Glare IS light that is viewed at the light source (luminaire),
which reduces one's visibility.
• Glare is caused by the contrast between a bright and a dark
area or object.
• Glare has a strong effect on the normal visual function,
causing a serious threat to safety.
• Luminance higher than 10,000 cd/m² causes visual
discomfort

6. GLARE CAN BE MINIMIZED BY:
• 1. Reducing the contrast - eg. Painting the background walls white.
• 2. Adding extra luminaires - to brighten up darker areas which will minimize the
contrast between darker and brighter areas.
• 3. Reducing the lamp wattage - extra luminaires may be needed to compensate
for loss of light levels.
• 4. Positioning of luminaires - if the luminaires are spread evenly over the area to
be illuminated.
• 5. Aiming - if the luminaires are aimed away from the normal viewing angle of the
occupants, this will reduce the contrast.
• 6. Shielding of luminaires - adding shields/baffles or allowing natural objects
(hedges, flowers etc) to stand between the luminaire and the occupants.
• 7. Creating distance - if the luminaires are moved away (eg. Used on higher poles).
• 8. Changing the colour of the light source – eg. Generally HPS is regarded as
causing less glare (but is also less effective) than white light.
• 9. Using a larger luminaire – eg. Using a 400w lamp in a 1000w reflector.

7. SKY GLOW
• Sky glow IS THE light reflected from the light source, road or other
surfaces up into the atmosphere.
• Sky glow in effect reduces one's ability to view stars in the night sky by
casting unwanted light into the atmosphere.
• Though this is not a safety or security issue, groups such as the
International Darksky Association (IDA) have mounted strong campaigns
to reduce sky glow and protect visibility of our night sky.

8. SPILL LIGHT
• Light that falls outside the area intended
to be lit.
• It is typically measured in lux in a the
vertical plane with the light meter
oriented towards the light source.
• Any light in these areas is not functional.
In some cases, they can even be a
nuisance for the surroundings, for
instance, by bothering house tenants
whose houses get included in the spill
light area.
• Spill light are objectionable and highly
offensive in others area or property line
• Florescent tube and street light has lot of
light spill.

9. Incorrect and correct installation
of optics and diffusers
INCREMENT IN LIGHT POLLUTION REDUCTION IN LIGHT POLLUTION

10. DEALING WITH LIGHT SPILL
• For internal lighting, the spill is usually redirected back into the
target area by reflectances from the wall, roof, etc.
• The primary control of light spill is at the design stage. Light spill can
be minimized by the use of appropriate luminaires and their
location, height and aiming. The spill can be predicted in advance.
Luminaires with precise optics can minimize light spill.
• Adding shields and baffles or natural objects (hedges, walls etc) can
further aid the process.
• To avoid light spill, it may be required to use asymmetric luminaires
near the ‘sensitive’ perimeter to prevent any back spill.
• The most effective way to minimize spill light
From a location is to apply forward throw
optics around the perimeter.

12. CONTROLLING SPILL LIGHT BY ADJUSTING
HEIGHT
• Higher mounting heights can often be more effective in
controlling spill light,(i.e., Narrower beam) may be used,
and the lights may be aimed in a more downward direction,
making it easier to confine the light to the design area.
• Lower mounting heights increase the spill light beyond the
property boundaries .To illuminate the space satisfactorily,
it is often necessary to use floodlights with a broader beam
and to aim the floodlights in directions closer to the
horizontal than would occur when using higher mounting
heights.
• Lower mounting heights make bright parts of the
floodlights more visible from positions outside the property
boundary, which can increase glare.

13. HEIGHT ADJUSTMENT
Floodlight at a higher
mounting height with narrow
beam angle, resulting in less
spill light
Floodlight at a lower
mounting height with wider
beam angle, resulting in more
spill light

14. CUTOFF CLASSIFICATIONS

15. • Maintaining an effective balance
between the reduction of light
trespass and the provision of
quality, beneficial lighting requires
thoughtful design and the selection
of luminaires with cutoff or full
cutoff optical systems.
Lighting design with full cutoff
optics will typically reduce skyglow
and spill lighting.
Moreover, it will reduce veiling
luminance (glare) from the
luminaire on and off the roadway,
thus improving overall visibility.
OPTICS

16. BEAM ANGLE
• The beam angle is the degree of width that light emits from a light
source. In other terms this is the angle between the two points on the
beam axis where the intensity drops to 50% of its maximum.
• Because after imax the light will fade and will not be part of the
highlight, the light after the imaxis spill light. And the human eye will see
mainly the beam angle
• There are many different beam
angles with different names,
the most common angles are
• 5°,10°,15°,24°,35°,45°
• Narrow spot 7°
• Spot 14°
• Flood 28°
• Wide flood >45°

17. BULB
REFLECTOR

18. Spill Lighting Are Used For And