Just a quick shot that I thought did a decent job of showing how f-stops can effect the composition.
This was taken at ISO50 1″ f2.6 on aperture priority
the point I’m focusing on is intended to be the 5-way nav button on the phone. With a wide aperture (small f#) the focus is more tightly centered on point of interest, and the other keys are increasingly out of focus as the move away from the 5-way. This adds “drama” (like I don’t have enough in my life).
Compare to this other image with a narrow aperture. (ISO 50, 1/4 f8.0)