1. Turn on Mental Ray

2. Create a camera, name it shotCam

3. Open Hypershade and click on the Cameras tab

4. MMB – Drag shotCam into the work area

5. Open the create panel on the left, expand mental ray > lenses, click “mia-lens-bokeh”

6. MMB drag “mia-lens-bokeh” onto shotCam, int the pop-up, click “dafault” for the input

7. In the Attributes editor you can play with the attributes of “mia-lens-bokeh”

Plane: This is the focus distance ( distance from camera to object you want in focus)

Radius: Larger = blurrier (bokeh amount)

Samples: increase to make it less grainy (bokeh quality)

Link to info about shader

To help with figuring out the focal distance:

when you create the camera also create a distance tool

Label the first locator (cam_loc), the second locator (cam_focus) and the distance (cam_distance).  Then in the outlier drag the locators and the distance under the camera.

You can the move the focus locator to the thing/area you want in focus. This is the value you place in the plane attribute of the lens shader.