This is a great exercise for everyone who wants to get beyond the automatic setting of his/her camera. I ask you to pick a subject, set your camera on “Aperture Mode” and then take three shots of your subject using your lens wide open, halfway closed and closed down. The best way of doing this is to mount your camera on a tripod and use a smartphone, tablet or any other remote release to trigger your shutter in order to get three identical placed images. Also, try to manually focus on your subject so that the auto-focus on your camera does not change the focal point when you change your aperture setting. And last, use the same light source and setting for all three images.
I used a 180mm macro lens at f4, f8 and f22. I totally controlled the camera from my tablet which was mounted on carbon fiber tripod with a heavy head to ensure stability. Now compare the three images. I manually fosucced on the center of the grape. Now compare the three images and notice the differences.
Enjoy and keep on photographing