pgatsky wrote:just to add to my last message is that it doesn't always do this which is making me think its a bug? Ive also seen Arthur Whitehead on you tube whos a big fan of using Octane use this method in backgrounds so its not just me.
You are running into a limitation of 8 bit color space. You can try adding noise to your gradient to help break it up, but it's a basic reality of the extreme ends of only a moderate available spectrum, particularly the dark end. Tom Scott just did a nice explainer video about it.
https://www.youtube.com/watch?v=h9j89L8 ... e=emb_logo
That's why you might want to render 16 or 32 bits/channel out of C4D/Octane, then you can choose how to tweak your color curves/noise in post to alleviate the banding.
I suspect that Ahmet's suggestion of using an actual 16/32 bit Image texture for the background will essentially add noise/dithering to the gradient in the render, so that when the render buffer is boiled down to 8 bits for saving, you don't have to mess with doing so in post. It might not give you as much control as rendering to a higher bit depth, but it is a lot simpler, and may be all that you need.
