The distribution of illuminance on a plane can be represented by isolux lines, i.e. points of equal Illuminance oined together to form a curve. The areas between the curves relate to intermediate values of illuminance. The increments selected for the individual isolux lines must offer a meaningful picture for the whole range of illuminance (e.g. increments of 100 lx). A sector with very dense curves represents an area with pronounced differences in illuminance, whereas ample spacing between the isolux lines indicates a high degree of Uniformity in the pattern of illuminance.