Since I'm spending quite a lot of time on the wider side of the aperture setting (which gives me shallow depth of field), I thought I would mention that the focal length of the lens and the camera to subject matter distance will also affect the depth of field. As I mentioned before, my focal length is 50mm since I'm using a 50mm prime lens. Therefore moving closer or further away will affect the DOF. I have this affinity to macro and close-up photography so I have to force myself to step back now and again.
You can see this distance difference in images 5 & 6 below. Every day I've been learning something new. If you were not already aware of this, give it a try and find out for yourself. Since I'm an amateur I was not aware of this, but now I can see how I can use this knowledge in the future.
When you focus on your subject, the further your subject is from the focal plan (sensor) of your camera the more depth of field you will have using the same f/stop and lens. See images below.
Here is a great article that goes into more detail atr lightstalking.com called: Depth of Field Simplified