I have found the greatest tool to understand depth of field and even shutter speed.
This company called CameraSim has a wonderful tool for showing you the differences between different apertures and different shutter speeds.
It works on not only your computer...but your iPad, iPhone and more.
Not only is it free to try....it really works.
http://camerasim.com/camera-simulator/ is the website or just click on the links below!
CameraSim Apps (compare all)