Ok Little brother, and anyone else who happens to read this blog, I am giving lessons today! This lesson is about Depth of focus and the art of photography, If you look at this first picture you will notice that pretty much each stem of the Crocus shoots pictures are in sharp focus. This is what many professional photographers would call "snapshot" it's a pretty picture and the subject is in focus, but to the professional, the pictures is cluttered and has no attention drawing point in it. Go ahead and click on it and see a bigger version of it to study it a little bit.
Now we come to the next picture and you will notice that there seems to be a huge portion of it that it out of focus, and indeed, there is. What has happened is that the depth of focus has been shallowed out to the minimum of the lens set-up. Because it isn't a specifically designed "macro" lens, the minimal depth is about 1.25 inches, rather than millimeters, however it is what I have to work with so it will do. As you look at the picture you will notice that the very front stems are in focus, from the ground to the tips. Both the foreground and the background of the picture are out of focus and the eye is naturally drawn to the sharp field. The Camera has not been moved from the first picture, only the F-stop has been changed thereby narrowing the focal plane. Go ahead and click on it and study the larger version for a minute or two.
Now we come to the 3rd picture and this time the focal plane has been shifted to the center of the group. Again the eye is drawn to the sharply focused stems in the center of the field. Notice that the white stripe in the center of the bent stems is in clear focus, making it very easy to identify these stems and the blades of the Crocus plant. Would you have as quickly noticed that in the first or second picture? Maybe, but probably not, and now there is now doubt what you are looking at, because it was brought to your attention by the selective focus.
Now we come to the last picture where the focal plane has been moved to the back of the group. Does it do anything special to the picture, other than making the front really fuzzy and the tips in the rear sharp? Not really, because there is really nothing in that area to show. So why show you this picture? Because it shows you that you weren't really missing anything from the other two. Generally it is quite expected to soften the areas of macro pictures that don't have any specific details to look at. The goal is to direct the eye of the observer to the interesting parts of the picture and keep them from wasting time on the useless background.
I hope this gives you a better understanding of the uses and desirability of the soft background in photos. I also hope that perhaps you will take notice of it and how it is used in the pictures you see around you day to day. There are many places where it is desirable to have perfect, crisp, clear focus throughout the entire picture, such as landscapes and forensics, but for Portraiture of specific artistic subjects, sharply focused pictures are a detriment.