Scatter diagrams of the core asymmetry ratio against field strength. Upper two rows: observations, using the full field of view. The abscissa is the magnitude of the apparent longitudinal flux density measured from the Fe I 6302 Å magnetogram, in arbitrary units and after 9-pixel spatial smoothing to mimic field spreading with height. Bottom row: smeared simulation. The abscissa is the magnitude of the vector field at height z = 500 km. Left: Mg line. Center: Na line. Right: Ca line. The sampling wavelength in kms^-1 is specified in each panel. The V/R values are multiplied by 1000 for plotting reasons. Density contours replace individual pixels to avoid plot saturation. The solid curves are the distributions over V/R and field strength, respectively. The dashed curves show the first moments per bin per axis. They line up for high correlation and are perpendicular at no correlation.