Relative difference on the convergence angular power spectrum depending on the derivation step used in the infinitesimal method (see Sect. 2.3.1) to compute the lensing distortion matrix at z = 1.9, using Healpix with N_side = 4096. Using a larger derivation step considerably biases the estimation of the power spectrum, while smaller steps mostly affect the very small scales. Our choice for h seems ideal as it is stable for ℓ < 10³ and should not lead to any large bias at smaller scales.