Simulated convergence quality of F&F as a function of image S/N, for half-wave (319 nm) PVE LWE at awavelength of 677 nm. Top image row: Initial DTTS images at specific S/N, showing increasing visibility of the aberrated first Airy ring. Bottom image row: Final noiseless images after 25 F&F iterations, showing acorresponding improvement in final PSF quality. Main panel: Plot of final Strehl ratio (red) and residual RMS wavefront error (blue) as a function of initial S/N. Each point is the average of ten simulations. The black horizontal line denotes both the starting Strehl ratio and wavefront error RMS, of 74% and 59 nm respectively. The shaded red line shows the Strehl ratio behaviour for F&F using the full 32  ×   32 pixel DTTS image as input (i.e. without an adaptive spatial filter), with the shaded region below S∕N = 20 denoting the region where this implementation diverges.