Adjusting settings for depth of field and blum

I'm using 2018 and all the post processing effects are working fine except depth of field- no matter what settings I try, I get either a totally blurred image or not the right amount. I'm just trying to blur the background behind a main image. I looked at the Unity info and its not helpful- also looked at older videos not helpful either. The blum is affecting some materials and not others and trying to understand why. I'm using Standard materials w/ real time lighting. Any help is appreciated, thanks

 

Nevermind- I got better results using the Legacy Blur, but still not able to control the Blum to affect only certain parts of an object- it seems o just do it overall so maybe a different effect is neeed

 

Switching to Linear color space activated Blum