log g versus effective temperature (top) and helium abundance versus effective temperature (bottom) showing the impact of metallicity in these parameter spaces. Circles and squares mark the helium-poor (log n(He)/n(H) < –1.2) and helium-rich (log n(He)/n(H) > –1.2) stars, respectively, for fits fixed to a metallicity of log z/z_sdB = 0. Grey and bronze triangles, oriented such that they point down and up, respectively, show the parameters derived for these same stars when fixing the metallicity to log z/z_sdB = − 0.3 and +0.3, respectively. Each triangle is connected by a black line to the circle or square to indicate the shift.