Field guide
Blur, pixelation and mosaic are not the same damage
A blur mixes neighbouring samples; pixelation replaces an area with fewer samples; a mosaic deliberately groups those samples into blocks. Their information losses are different.
01
Motion blur leaves directional traces that can constrain an inverse estimate. Defocus spreads points in discs, often with a radius that changes across the frame.
02
Pixelation discards within-cell variation. Enlarging a block smoothly can remove the staircase appearance, but it cannot reveal the original values that were averaged away.
03
A censorship mosaic is designed to destroy identity. A model may invent a plausible face or word, but plausibility is not recovery and should never be described as such.
04
Inspect the frequency pattern before choosing a tool. Regular grid peaks favour a block diagnosis; elongated edge echoes favour motion; neither should be treated with ordinary sharpening alone.