Most of today’s digital cameras focus automatically for you. And depending upon the type of photograph you take, most of it might be in focus…and some of it may not be in focus. Why is this. We “old” photographers call it “the depth of field,” or the part of the photograph that is in focus. Today’s photographs call it “a slice” of the photograph that is in focus.
If you have an automatically focusing camera and the camera determines your exposure and shutter speed, everything is done for you and all you have to do is to aim and shoot.
The rule of thumb is that the further away from your subject, the greater amount of the photograph will be in focus. The closer you are to a subject, the lesser amount will be in focus. That is ok if you are taking a photograph of a group of people in a straight line…or nearly in a straight line. But if you are taking a closeup of a flower or a subject, just a small amount of the photo will be in focus and the rest will be out of focus.
On my landscapes I always try to get something close up to frame the actual subject. On non zoom lens you can set your lens opening and shutter speed to to change the depth of field. On a zoom lens with digital cameras you will need to focus in the middle of your subjects if you are trying to frame your photograph and want both the foreground and the background to be in focus.
Sounds simple but not always. With your zoom lens set to a wide angle mode you will get more in focus than you will in the telephoto extended all the way out. I may have confused you here, but a person could write a book on the depth of field issue.
I have included two photos with this blog, one of a Mission in San Antonio taken in 2011 and one of a cruise ship at harbor in New Orleans taken in 2010. In the mission photograph, the tree branch is in fairly good focus, not as good as I would like, because I was close to the tree. In the cruise ship photo, the bridge, which frames the ship and gives us an idea of its large size, is in focus as well as the ship itself. Even though this was taken with the zoom quite a ways out, the fact that I was a distance away from the bridge and the cruise ship, everything is in focus.