Visible color stripes instead of smooth gradients — result of low bit depth or aggressive compression. 8-bit material shows this badly in skies and skin tones.
Banding occurs when continuous color gradients break down into visible bands — instead of smooth transitions, you see abrupt edges between shades. On set or in editing, this becomes particularly annoying with skies, skin tones, and water, where the eye immediately registers any false jump. The cause lies in the color depth: 8-bit material only has 256 levels available per channel. That sounds like a lot, but it's not enough if you later perform aggressive color correction, increase contrast, or run multiple compression steps consecutively.
The practical side: You often don't notice banding until late — in the grading suite, when you want to push a subtle gradient upwards and suddenly the entire image breaks down into bands. It becomes particularly treacherous with chroma subsampling (4:2:0 instead of 4:4:4), which discards color information anyway. If H.264 compression or aggressive noise reduction are added, the problem is compounded. 10-bit material — whether ProRes or DNxHD — gives you significantly more leeway. With 1024 levels per channel, you can grade much more radically without banding becoming visible. This is the real difference between consumer and broadcast formats.
On set itself, you can minimize the risk: expose correctly to optimally utilize color information — not underexposed, not overexposed. Bright skies with low saturation colors are particularly susceptible; a subtle texture or a LUT can help to visually break up banding. In editing, it is advisable to work with higher bit depths (10-bit or even 12-bit for RAW material). If you are working with 8-bit source material, perform color correction in 32-bit float — the computer calculates internally with much higher precision and posterizes less visibly in the end.
A practical tip from daily work: Banding can never truly be corrected, only avoided. Therefore, the old principle applies — capture correctly, grade carefully. If you notice that your material tends towards banding, it's usually not the grading's fault, but rather that too much color depth was lost during recording or archiving.