Many thanks for all your replies and the link given. I wasn’t too sure how to describe the problem so wasn’t too confident what to search for!
The screenshot that I posted was originally a Quicktime file using the Animation codec rendered in Cinema4D. Those are perfect quality. I really am a bit confused. I seem to have adjusted every setting with no luck. The PNG codec works fine but they don’t really give a smooth playback on the laptop we’ll be using.
I’ve decided to just used MPEG2. Even though there’s a bit of a banding effect on the gradients (something that I also can’t seem to solve) it’s good enough.
Thanks for your help!