Can someone please tell me how to fix this? I dont care for this banding effect. I export png image in 16 bit color format. I dont know how to fix this.
it probably is fine in your actual render, just that monitors have a limited range of colours… in the render settings under post processing set dither to 1…
info about dithering – http://en.wikipedia.org/wiki/Dither
This is applied after compositing so you should be able to set up a simple node network to dither the rendered images