Most Iray HDRI environment sets don't allow 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.
With UltraHD Iray HDRI With DOF - Holliday houses, you'll get 1 ultra HD (up to 16K) custom-made environment with or without the depth of field presets. This environment is a small street of a village located on the Ile d'Aix on the Atlantic ocean, with its typical colorfull houses.
Home Page: _https://www.daz3d.com/ultrahd-iray-hdri-with-dof--holliday-houses