Depth of Field

The Depth of Field (Deprecated) component is confusing. The part I am confused with the most is the transform selection. I have no idea what to set it to, to create another object without a mesh renderer and have it at x distance, to set it to a box half way across the map? I have tried using google to find my answer but nothing I have found have really gave me any clue on what to do.

Thanks.

For any future reference, the transform means that wherever that is, it will focus on. The best way to get the first person DoF effect would be to cast a ray and have an empty gameobjects position be set to hit.point, and the empty gameobject be the transform