Encircled energy of the power spectrum of the 361 × 361 pixel inset, centred on the centre of the solar disc, of the test continuum filtergram, before (black), and after image restoration with K₁ (blue) and with K₂ (red). The green series gives the encircled energy of the mean power spectrum of the synthetic intensity maps corresponding to μ = 1.0. The vertical dashed line marks the cutoff spatial frequency (see text) of the restored (with K₂) test continuum filtergram and the horizontal dashed line the encircled energy of the mean power spectrum of the μ = 1.0 synthetic intensity maps at this spatial frequency. The dotted line denotes encircled energy of unity.