I have used this atmosphere before, I am recalling that clicking volume under mat room lets it work. Sound like you did that. Then under properties on your chosen light, click atmosphere on. Sound like you did that too. Set the value there very low. I am recalling .003 or .3 or .03 or some such. (sorry I'm at work.) Make sure you have a full background set of objects or planes that are behind where you want your effect. It can't render atmosphere over emptiness. It sounds like you knew that one too, if your objects are turning white. The key was that atmosphere strength dial in the light properties. It just needs to be set very low. Also, other bright lights will wash out this effect. Don't know about the depth of field though. Hope this helps. p.s. I think it has to be spotlight.