Illustration of the ring finding process for two simulated Einstein rings from the Bologna Lens Factory (Sect. 4). For each row from left to right are shown 1- an example of simulated Einstein ring (64 × 64 pixels), along with its lens galaxy, 2- the lensed ring after PCA subtraction of the foreground galaxy, 3- the result of curvelet denoising, 4- the polar transform of the ring revealing a visible horizontal line whose position along the y-axis gives a measurement of the radius of the Einstein ring.