Sometimes called moiré or a glitch, aliasing is a phenomenon where a digital camera has trouble translating an intricate pattern. Aliasing can result in a number of odd visual artifacts in photos or videos. For example, a person’s finely striped or patterned shirt can cause strange waves or swirl patterns to appear over it in a digital image. The waves or swirls, called a moiré pattern or moiré effect, are just one type of possible outcome. Aliasing can also cause color noise, tone jumping (random color changes), or jagged edges or pixelation across lines and boundaries (sometimes called jaggies).
“Aliasing is basically an artifact that makes an image look particularly digital in a disagreeable way,” says photographer Philip Heying. “It’s caused when digital information is broken down into pixels and bits; little tiny particles that are laid out in a grid. Sometimes, when information that you’re seeing in the real world meets that grid of the digital world, it’ll cause this objectionable moiré pattern or strange color shift that doesn’t look like what you’re seeing.”