Read polar candela charts
Understand the candela distribution polar plot, including the C0/C180 vs C90/C270 planes and how peak intensity is shown.
4 steps · 3 min read
The polar plot is the single most-used photometric chart in lighting design. Once you can spot symmetry, peak intensity, and beam shape from a polar plot, the rest of the photometric tools click into place.
Open the Photometric tab
From any luminaire in the library, switch to the Photometric tab. The first card on the left is Candela Distribution — the polar plot.
Identify the planes
The polar plot overlays two planes by default: C0 / C180 (the "lateral" plane, drawn in blue) and C90 / C270 (the "axial" plane, drawn in red). For a symmetric fixture they overlap; any difference between them tells you the fixture's beam is asymmetric.
Angles around the perimeter are vertical angles measured from straight down (0°) to straight up (180°). The radial scale is candela.
Read peak intensity and beam angle
The peak of the curve points to the angle of maximum intensity. The radial value at that peak is the peak candela (cd). Beam angle is the cone within which intensity stays above 50% of peak — for a downlight that means the angles where the curve crosses the half-peak ring.
Compare to the linear plot
The Linear Plot card next to the polar plot shows the same data on a Cartesian (vertical angle vs candela) axis. It's easier to read precise candela values from the linear plot, while the polar plot makes the *shape* of the distribution intuitive at a glance.