Deliberate noise addition during color reduction or quantization — masks banding artifacts through grain. Essential when mastering for lower bitdepth.
Dither
You're sitting in the grading suite and suddenly notice: the colored areas of your 10-bit master look like stairs when exporting to 8-bit. Horizontal lines in the sky where there should be continuity. That's banding – and that's where dither comes in. It's not magic, but deliberate noise: you intentionally add high-frequency grain to mask these visible color jumps. The human eye perceives the fine noise as structure rather than a hard edge.
In practice, it works like this: when you reduce from 10-bit to 8-bit – for example, during DCP mastering or HDR-to-SDR mapping – you lose gradations. Instead of smoothly transitioning, the color brutally jumps to the next available palette stage. Dithering solves this through controlled quantization noise. You don't just take every value – you distribute it pseudo-randomly across neighboring bit planes. Ordered dithering creates a regular pattern (Bayer matrix), while error diffusion like Floyd-Steinberg distributes quantization errors to neighboring pixels. In DCI mastering, we mostly use error diffusion because it appears more natural.
You don't need to think about this on set – that's for editing and mastering. But as a DoP, you should know: the cleaner your gradient in the original, the more aggressive the dithering can be. A noisy shot requires more subtle dithering, otherwise, it will look doubly grainy afterward. In grading, we deliberately use dithering at the end of the pipeline – after color correction, after windowing, just before export. Some NLEs have built-in dither modes (Resolve offers several), as does some motion graphics software. The strength is a trade-off: too little dither = banding remains visible. Too much = your film looks like old VHS with noise gate artifacts.
Important: Dithering is destructive. Once applied, the noise is in the output. You can no longer remove it. That's why you only dither during the final export, not in your intermediate DCP caches. HDR formats (Rec. 2020, DCI-P3 in 12-bit) require less aggressive dithering than old broadcast standards. And: don't confuse it with noise reduction – that works in the exact opposite way.