The isofootcandle plots graphically represent the luminaire's lighting pattern, in illuminance, striking a horizontal surface.
EXAMPLE MAXIMUM CANDELA POINT and lateral angle line is included here to illustrate how illumination levels at a point correlate the Isofootcandle Plot information shown.
The point represents a calculated 2.95fc, which corresponds to its position between the 2fc and 4.1fc Isofootcandle contour lines (at a 14' Mounting Height).
During the Schematic Design phase of a project, rough luminaire layouts can be created using isofootcandle plots.
To estimate a fixture layout - start from the perimeter, where the 2.0fc isofootcandle trace crosses the Reference Line, to establish the maximum single fixture distance to the site perimeter (1.6 MH, figure 11.1).
By overlaying Isofootcandle Plots, a rough idea of illuminances can be accomplished by adding the values of each contour where they intersect (figure 11.2).