DoF effect is too weak, everything is sharp even if I set very low f/stop values such as 0,1This may be caused by using wrong scene scale. Incorrect units may be used. The dimensions of objects in the scene should correspond to the size of camera's sensor width. If you are, for example, using millimeters instead of meters (or vice versa), you need to either rescale the scene or set camera's sensor size to corresponding units (for example meters instead of millimeters).