Most Iray HDRI environments set don't allow the depth of field use easily and DIRECTLY out of the box. UltraHD IRAY HDRI With DOF does!
You won't have to tweak anything as all the presets are there for you to just click and render.
What you'll get is 1 ULTRA HD (up to 16K) custom-made environment with or without the Depth of Field presets.
This environment is a picturesque and touristic landscape featuring the ocean, a harbor, medieval towers in the back, a distant old city, and a unique globe statue, all perfect for the most scenic postcard or fun tourist selfies.