Artificial color banding — loss of tonal gradients when bit-depth collapses or aggressive color quantization happens. Results from codec artifacts or aggressive grading on low-bit footage.
You know the drill: you're adjusting curves in grading, and suddenly unnatural color blocks appear instead of smooth transitions. That's posterization—and it happens faster than you'd like when you're working with footage that doesn't have enough bit depth or has been aggressively compressed.
The technical reality is brutal. Every color in a digital image is defined by numerical values. With 8-bit per channel (RGB), you theoretically have 256 levels per color—that sounds like a lot, but it's damn little when you start grading in post-production. Every curve adjustment, every levels tweak, every LUT application—you're re-quantizing the values. The fine gradients in skin tones or skies become visible bands. The eye sees it immediately: it looks cheap, digital, artificial. It becomes critical, especially with natural shots featuring a lot of sky or water.
There's little you can do about it on set, other than anticipate it in the format: Log footage (like Alexa LogC or DaVinci Wide Gamut) stores more color information, even if the file is 8-bit—thanks to curve encoding. In editing and grading, your strategy is: work in higher bit depth (32-bit float in DaVinci, or at least 16-bit) before finalizing. This gives you room for aggressive grading moves without the quantization becoming visible. Another mistake: aggressive chroma subsampling (4:2:0) significantly exacerbates the problem—the color information is already reduced before you even start.
Practical tip from daily work: Posterization is also a sign that your footage has been compressed too much or that you had to shoot with a terrible proxy format. If you notice that the grading headroom is extremely tight, posterization often exists before you even open the grading window. In such cases, only one thing helps—a subtle dither effect or noise in the grading can mask the visible transitions. Not ideal, but better than blocky colors. Another term you should know: banding—this is practically the aesthetically visible phenomenon of posterization, especially in skies and color gradients.