Remove banding in After Effects

It's a bit of a mystery why there's still so much banding in TV & web graphics. Maybe people can't preview in the appropriate color space or codec to see banding, which may be eliminated by adding a Noise filter at about 5% (maybe on an adjustment layer). The stuff on cable systems is subject to God knows what compression and recompression, so being conservative with gradients may be the better part of valor.

After Effects Help has an additional tip, which reinforces thinking about delivery codecs:

"Even if you’re using 8-bpc footage and are creating movies in 8-bpc formats, you can obtain better results by having the project color depth set to 16 bpc or 32 bpc. Working in a higher bit depth provides higher precision for calculations and greatly reduces quantization artifacts, such as banding in gradients.

Note: Merely increasing the color depth within a project won’t eliminate gradients if the output format has a low bit depth. To mitigate banding, After Effects introduces dithering of colors when the colors are converted to 8-bpc colors, including when rendering and exporting to an 8-bpc format. This dithering is not introduced for previews. To force dithering for previews, apply an 8-bpc effect that does nothing—such as the Arithmetic effect with the default values—to an adjustment layer."

Some other workarounds (creating gradients, TV vs. web) were discussed by Greyscale Gorilla in 2009; see How to Remove Banding Artifacts in After Effects:

How to Remove Banding Artifacts in After Effects from Nick Campbell on Vimeo.

Even when the video is final, you may still be able to fix banding issues with a plug-in like Magic Bullet DeNoiser or similar. Here's a tutorial on removing banding with Deband from GenArts Sapphire for After Effects:

Update: for additional perspective and details on some codecs, see Color Bit Depth by JD Vandenberghe on PVC.