Spotlight with Halo applied is creating rings around light Here's a portion of a render I'm working on, which is backlit from behind by a spotlight with a "Halo" effect applied:



If you look carefully in the background, you'll notice the halo effect is creating "rings" of shadow as it fades.  How can I remove these rings and make the halo effect fade out smoothly?  I've played around with all the settings I can find without any success.

Here's my current settings for the spotlight:
That is a dithering problem. Which is not really a problem at all, but rather what physically must happen. That occurs any time there is a small change in color spread over a large area.  

One of the ways to get rid of the banding is to make a stronger contrast, such as a pure black background.

The best way to deal with it. Is under the Render tab in the Properties window. Set the dithering amount up a bit until the color banding is not visible.