I don’t know, I’m afraid - but it’s easy enough to use. Select an object where you want to have it sharp. In the Render Options, enable to Premium and Depth of Field. Then click on Set To Current Selection. This gives you the distance from the camera to the object. It is called “Focal Length” which is a misnomer. “Lens Radius” (another funny name for the f-stop) lets you adjust a wide or narrow DOF. The smaller you put that value (smallest is 0.001), the wider the range of focus. It does work like the f-stop. Smaller apperture greater range, larger apperture smaller range. You’ve got to experiment with this a bit. I hope this gets you going.