Unfolded Physics on Instagram: "This is a practical demonstration of the moiré principle, an interference effect that appears when two repeating patterns overlap with slightly different spacing or timing, producing a larger, slower pattern that is not physically present in either one. In this clip, the ruler’s edge and fine surface details become a fast moving, repeating pattern as it vibrates. In shadow, the lighting is effectively more directional and higher contrast at the boundary, so small

Moire effect removal - Lightroom Tip