You can view the calculated distance of the camera from the object and apply that value to the  for the camera to achieve  in the Camera’s . 
         
         For information on depth of field, see Focus and blur.
         
         Note 
                  - To create an image that has wider depth of field (more area in front of and behind the subject that is in focus) use high
                     fStop values, such as f16, f22, f32. To achieve narrow depth of field (less area in front and behind the subject that is in
                     focus) use low fStop values such as f2.8, f4 or f5.6. For more information on fStops, see fStop (aperture) and shutter speed/angle.
                  
- Depending on the fStop and  values, parts of the object may or may not be in focus.
                  
 
         To ensure the center of an object is in focus for Depth of Field
         
         
            - Select the object in the view.
- Make sure  is turned on in the  menu. ( is on by default). Notice the  value.
            
- Use the  value as the  value in the  section for the current Camera.
               If you select multiple objects, Maya uses the center of their bounding box to calculate the distance from the camera.