Variation of MGE-predicted luminosity distributions with bar position angles ψ_bar. All distributions are deprojected under the true viewing angles (θ, φ) = (θ_T, φ_T) = (85° ,50° ). From top to bottom, the panels show the normalised luminosity distributions in the intrinsic x-y, x-z, and y-z planes. From left to right, the bar position angles are ψ_bar = 91.0°, 92.5°, and 94.0°. The middle panels with ψ = 92.5° correspond to our chosen distribution and are the same as the middle panels in Fig. 4. The bar axis ratios p_bar in the x-y plane and the values of the parameter ξ (defined in Eqs. 11–13) are labelled in the figure. The lines, arrows, and labels in the central panel illustrate the calculation of ξ_xz: we first divide the x-z plane into 1 arcsec-wide slices along the z-axis; for each slice, we calculate the brightness ratio between the brightest pixel and the central pixel, and finally select the maximum ratio across all slices as ξ_xz.