Doesn't matter if it's set to Normal, Best, with or without Alpha, ProRes 422, ProRes4444XQ, Normal Gamut, Wide Gamut, export directly from Motion, send to Compressor, Dither, Anti-Alias - They all fail and they all have nasty banding! Why?
This is a year later and this problem is still not fixed. Actually, a quick Google search shows this problem creeping as early as 2011.
https://forums.creativecow.net/thread/170/870329
https://discussions.apple.com/thread/3310058?start=15&tstart=0
http://www.fcp.co/forum/4-final-cut-pro-x-fcpx/16928-prores-banding-in-quicktime-player-not-in-motion-or-fcpx
https://forums.creativecow.net/thread/344/39931
That was the early Motion version 5, we are now at 5.3.2
Anyway, as it is Motion is useless as soon as you want to lit your scene. No light, all is good and dandy. Add a Light Object, all goes down to the drain 'cause... ugly banding.
And no, adding noise is not a fix. Adding noise does not clean the banding away. It just adds noise and your graphic is all dirty instead of clean with a smooth gradient.
Indeed, exporting using Compressor Settings and selecting Animation Codec results in a smooth gradient. And because of the codec, QT Player has to convert the file before opening it.
Mind you it looks perfect in Motion's Canvas, but on QT export, ugly banding all over. Exporting a single frame as TIFF or PNG looks just fine though. So why? Why can Motion export a still perfectly but not a .mov?
See for yourself (click on images to see larger versions):
Motion Canvas, just fine.
QT export (ProRes4444XQ Best) - Terrible ugly BANDING!
Exported as single PNG - No banding, looks just fine
Rahhh! Now I have to recreate my graphics in After Effects.
I resubmitted feedback to Apple. Do so yourself if this is driving you crazy as well.
