Flowers and depth of field

I had a great time on Saturday morning taking some pictures of a rose in my garden. As I was taking them one of the things that I was experimenting with, was depth of field, specifically the aperture. Aperture is the size of the hole the opens in the lens to let in light. The larger the hole, the more light gets let in. The aperture is measured in f-stops, which relate to the area of the hole. Each "stop" lets in half the light as the previous one, but because of how it is calculated, the numbers aren't as simple as 1, 1/2, 1/4, 1/8 etc... Instead it's 2.8, 4, 5.6, 8.0, 11, and 16

Anyway... larger apertures have some good things associated with them - more light, faster shutter speed, or lower ISO. However, as with all things, there is a downside. The larger the aperture (smaller number) the smaller the depth of field. In other words, less of the picture is in focus. Look at the two pictures below.

This first picture was taken at f/16, 1/25th of a second shutter speed. As you can see, the flower is sharply in focus, but the fence is also in fairly sharp focus too.

This picture is f/5.6 - 3 stops "faster". As you can see, the fence isn't nearly as in focus. It's much more blurred and, I think visually appealing.

This one is f/2.8. Notice how blurred the fence is - you can hardly tell what it is exactly. But also notice the flower. If you look closely, you'll notice that the depth of field is so shallow, that not even all of the flower is in focus.