Lighting schemes

Lighting Schemes
General principles of good lighting

 Not injurious, rather protect our health by minimizing eye strain.
 It must provide plentiful but glare free light for all kinds of tasks.
 Provision of spot lights for tasks like sewing, reading etc.
 No source of light should appear in the visual field of any worker during working
operations.
 As far as possible all lights should be provided with shades
 Prevent accidents especially at such hazards as in staircases.
 Ensure absence of harsh shadows.
 It must create sufficient contrast between dark and light areas to prevent dullness
and monotonous.
 Maintain aesthetic appearance, contribute beauty and individuality to home
Realization of these aims involves:
a) Careful planning of brightness and colour patterns within theworking
area
b) Using directional lighting to assist perception of task and to give good
modeling
c) Controlling direct and reflected glare from light source
d) Minimizing flicker from certain types of lamp
e) Installing emergency lighting system where necessary

Types of Lighting Schemes:
Lighting schemes are classified according to the location, requirement and purpose
etc. are as under :

1. Direct lighting

2. Indirect lighting

3. Semi direct lighting

4. Semi indirect lighting

5. General lighting

i. Direct Lighting:
 It is most commonly used type of lighting scheme. In this lighting
scheme more than 90 percent of total light flux is made to fall directly on
the working plane with the help of deep reflectors.
 Though it is most efficient but causes hard shadows and glare.

,  It is mainly used for industrial and general out-door lighting.

ii. Semi-Direct Lighting:

 In this lighting scheme 60 to 90 percent of the total light flux is made to
fall downwards directly with the help of semi-direct reflectors, remaining
light is used to illuminate the ceiling and walls.
 Such a lighting system is best suited to rooms with high ceilings where a
high level of uniformally distributed illumination is desirable.
 Glare in such units is avoided by employing diffusing globed which not
only improve the brightness towards the eye but improve the efficiency
of the systems with reference to working place.

iii. Semi-Indirect Lighting:

 In this lighting scheme 60 to 90 percent of total light flux is thrown
upwards to the ceiling for diffuse reflection and the rest reaches the
working plane directly except for some absorption by the bowl.
 This lighting scheme is with soft shadows and glare free.
 It is mainly used for indoor light decoration purposes

iv. Indirect Lighting:

 In this light scheme more than 90 percent of total light flux is thrown
upwards to the ceiling for diffuse reflection by using inverted or bowl
reflectors.
 In such a system the ceiling acts as the light source, and the glare is
reduced to minimum.
 The resulting illumination is softer and more diffused, the shadows are
less prominent and the appearance of the room is much improved over
that which results from direct lighting.
 It is used for decoration purposes in cinemas theatres and hotels etc.
and in workshops where large machines and other obstructions would
cause trouble some shadows of direct lighting is employed.

v. General Lighting:
 In this scheme lamps made of diffusing glass are used which give
nearly equal illumination in all directions.