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

How to Fix or Remove Moire Patterns Easily with Photoshop