Comparison between the luminosity-weighted kinematic tracer k_lum (vertical axis) and a purely photometric bulge-to-total ratio taken from Domínguez Sánchez et al. (2022) (horizontal axis). The contours (grey lines filled with the blue shaded colours) are drawn at probability levels with a constant spacing of 0.1 while the black dots represent the data. The vertical arrow on the right side qualitatively explains the meaning of the k_lum parameters: a greater k_lum value corresponds to higher rotational support within the galaxy.