Relative flux solution in SIR coordinates derived for the four grism-tilt configurations by the relative flux calibration. The value Δmag indicates the correction in magnitude that should be applied to the portion of a spectrum landing at the given focal plane position. The vignetting at the focal plane sides in tilted configurations RGS000-4 (top right) and RGS180+4 (bottom right) is apparent, as are large-scale features in common with the imaging flux solution (the so-called flat field, Euclid Collaboration: Polenta et al. 2026). This solution is found to be mostly achromatic and is therefore averaged over wavelength.