Left: Signal-to-noise ratio (S/N) as a function of the magnitude for the luminous sources detected in the Euclid simulated images of the galaxy cluster MACS J0416. Blue, green, grey, and magenta dots indicate the S/N for galaxies detected in the EuclidI_E, Y_E, J_E, and H_E images, respectively, as a function of their magnitude in the different bands. These quantities are measured within circular apertures of radius 0$\stackrel{″}{.}$65 for the I_E band, and radius $0\stackrel{″}{.}51$ (equivalent in extension to the $0\stackrel{″}{.}9\times 0\stackrel{″}{.}9$ aperture quoted in Table 1) for the Y_E, J_E, and H_E filters. Vertical and horizontal dashed lines mark the values of the limiting S/Ns ((S/N)_lim^I_E = 15.9, (S/N)_lim^Y_E = 6.5, (S/N)_lim^J_E = 7.8, and (S/N)_lim^H_E = 7.2) and limiting magnitudes (m_lim^I_E = 24.5, m_lim^Y_E = 24.0, m_lim^J_E = 24.0, and m_lim^H_E = 24.0). Right: Full width at half maximum (FWHM) distribution (grey) and its cumulative probability distribution (red) estimated for 1748 galaxies in six HFF parallel fields with I_E magnitude ≤ 24.5 (i.e. brighter than the limiting magnitude in the I_E filter).