Dithering breaks banding by adding a little calibrated random noise to a gradient before quantization, so that instead of snapping to one flat value, a region's pixels scatter between two adjacent values in a ratio that averages to the right brightness. The eye blends the speckle back into a smooth ramp and never sees a hard contour - the way a painter limited to a few tins fakes a continuous wash by stippling. Dithering attacks the perception, not the root cause; it trades a visible contour for invisible noise, which the eye vastly prefers. Natural film grain and sensor noise act as a built-in dither, which is why denoising or an aggressive encode can make latent banding snap into view. The crucial catch: do not dither just before a lossy encode and expect it to survive, because compression treats the dither as noise and quantizes it back out, and the bands return. Add it as close to the final delivered bitstream as possible, or raise the bit depth instead.
