Aliasing & Antialiasing

Aliasing, also known as moire fringing, describes the step-like edges that diagonal or rounded lines take on in digital images. This jaggedness results from the square shape of the individual pixels that compose an image. When a picture has been aliased, it appears distorted with rough edges. Generally, aliasing occurs with limited photo resolution, if an image is finely textured or if it contains sharply contrasting lines. Similarly, if a smaller image is blown up to a larger scale, it may be aliased as each pixel that composes the image becomes more apparent.

In contrast, anti-aliasing refers to more refined edges in an image. The process of anti-aliasing calls for an exchange of colors within a pixel at the edge of the figure to smooth the pixels’ squareness. By blurring the colors at an image’s edge, anti-aliasing produces crisper images.

Reducing the size of an image in a photograph can also invoke anti-aliasing because each pixel becomes smaller in size: consequently, the individual edges of each pixel become less discernable. Expert photographers tend to opt for anti-aliasing, as it produces clearer, more detailed, pictures. These days, most digital cameras come with anti-aliasing filters to limit the jagged effects aliasing can produce.