Banding

What you are seeing

A gradient in the real world is continuous. Stored digitally it has to be quantized into discrete values, and if the number of available values is too small relative to how gradually the colour changes, the transition renders as a series of flat bands with visible edges between them.

Skies, studio backdrops, soft shadows and blurred backgrounds are where it appears, because those are the regions that change slowly across many pixels. It is the artefact people most often notice without having a name for it.

Two different causes

The first is bit depth. An 8-bit channel offers 256 levels. Across a large area of very gradual change, 256 steps is not many, and the boundaries between them become visible. This banding was in the file before any compression happened.

The second is compression. Lossy quantization rounds the small differences that describe a gradual ramp, and once enough of them round to the same value the ramp collapses into steps. This banding is introduced by the encoder and gets worse as quality drops.

Distinguishing them matters because the fixes are different. Compression banding responds to a higher quality setting or a better codec. Bit-depth banding does not — re-saving at quality 100 preserves it perfectly.

How to avoid it

Work at higher bit depth while editing. A 16-bit working file has 65,536 levels per channel, and gradients survive heavy tonal adjustment that would visibly break an 8-bit file. Convert to 8-bit only at export.

Add a small amount of noise, or use an encoder that dithers. Noise breaks up the boundaries between levels so the eye integrates them back into a smooth ramp — this is why film grain hides banding and why a completely clean gradient is the hardest thing to store.

Choose a format that handles it. AVIF is markedly better on smooth gradients than JPEG at the same file size, and it supports higher bit depths natively.