Effect of HST PSF error and post-deconvolution isotropisation. Multiplicative (left panel) and additive (right panel) shear bias differences obtained when using two different HST TinyTim PSF models for HST conv and HST deconv and a pixel scale of $0\stackrel{″}{.}04$ (upper panels, test III), as described in Sect. 5.5. The lower panels show the results applying an extra rotation after the deconvolution (test III with rotat.). The data points show the bias obtained from the fit with the error bars indicating 1σ uncertainties for a number of galaxies N_gal ≃ 24.7 × 10⁶ for each S/N value.