Hasta La Motion!

Fairly, simple question to you.

I’m compositing some 3d elements with a gradient background, and adding DOF.

The problems is, before adding DOF, I set the "ramp scatter" in the background to a good amount (to prevent banding) but after I add depth of field, just because it "blurs" and "softens" all the areas at the background (focusing a foreground object) banding starts to happen again.

How can I prevent/minimise banding in these kind of situations ? For the time being, I dont want to leave this as it is now.