Different lighting schemes

 Different lighting schemes may be classfied as:

(i) direct lighting, (ii) indirect lighting, (iii) semi-direct lighting, (iv) semi-indirect lighting, and (v) general diffusing systems.

(i) Direct Lighting
As the name indicates, in the form of lighting, the light from the source falls directly on the object or the surface to be illuminated. 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) 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.

(iii) Semi-direct System

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.

(iv) 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.

(v) General Diffusing System
In this system, luminaries are employed which have almost equal light distribution downwards and upwards.