Illumination Notes
1
Methods for calculating illumination The problem of the lighting designer at the functional level is to determine how many lights and where to place them to get the correct level of illumination for a given activity. These calculations can be divided into two types • We want to determine the illumination at a small specific location in the room from a point light source. Accent or task lighting. This not much more complicated than exercises we have already been doing
Simply get polar plot for luminaire and work out the illumination on surface for a given lamp. Called the point illumination method.
2
The lumen method We want to estimate the illumination pattern from a set of diffuse lighting sources over a broad area in a room. This is a more complicated exercise. We will be using the total flux method, or lumen method to get rough and reasonable estimates of the lamps/luminaires needed. This method is used in areas where a uniform light intensity of the work area. Used for rectangular rooms with gridded luminaire pattern. Uniform: For the present discussion we require the minimum illumination level to be at least 70% of the maximum illumination level.
3
The lumen method
What we have to do is solve an equation of the type
Φ rec E= A where E is the illumination level required at the work surface and A is the total area of the plane where the work is done. The factor Φrec is the flux of light received on the working surface. The factor Φrec is not the flux emitted by the lamps although it will be related to the flux emitted by the lamps. The main issue is to determine how much flux needs to be installed, i.e. Φinst, to get the required amount of received flux Φrec.
4
Methods for calculating illumination The first step is to determine how much flux is to be received.
Φ rec = EA
Multiply the illumination required by the surface area. The received flux is related to the installed flux by a simple formula
Φ rec = MF × UF × Φ inst
Methods for calculating illumination The problem of the lighting designer at the functional level is to determine how many lights and where to place them to get the correct level of illumination for a given activity. These calculations can be divided into two types • We want to determine the illumination at a small specific location in the room from a point light source. Accent or task lighting. This not much more complicated than exercises we have already been doing
Simply get polar plot for luminaire and work out the illumination on surface for a given lamp. Called the point illumination method.
2
The lumen method We want to estimate the illumination pattern from a set of diffuse lighting sources over a broad area in a room. This is a more complicated exercise. We will be using the total flux method, or lumen method to get rough and reasonable estimates of the lamps/luminaires needed. This method is used in areas where a uniform light intensity of the work area. Used for rectangular rooms with gridded luminaire pattern. Uniform: For the present discussion we require the minimum illumination level to be at least 70% of the maximum illumination level.
3
The lumen method
What we have to do is solve an equation of the type
Φ rec E= A where E is the illumination level required at the work surface and A is the total area of the plane where the work is done. The factor Φrec is the flux of light received on the working surface. The factor Φrec is not the flux emitted by the lamps although it will be related to the flux emitted by the lamps. The main issue is to determine how much flux needs to be installed, i.e. Φinst, to get the required amount of received flux Φrec.
4
Methods for calculating illumination The first step is to determine how much flux is to be received.
Φ rec = EA
Multiply the illumination required by the surface area. The received flux is related to the installed flux by a simple formula
Φ rec = MF × UF × Φ inst