You can do this exercise on a computer using Photoshop or other programs or you can do it manually on a regular print. What I ask you to do is to draw a square around your subject and observe the difference a simple square makes in an image. If you are a Photoshop user you can also change the inside or outside of the square. As always, enjoy and observe!
I photographed this rose early in the morning. I darkened the part outside the square!