In the previous articles about depth of field, we learned about how to control depth of field. However, it is also important to know about situations where you should control depth-of-field. A lot depends on what results you want from your shot and how do you want to shoot it. What depth of field should be there is a shot completely is a photographer's decision. But, there are situation where a photographer's decision may go wrong. For situations like this please refer the points / tips mentioned below. These tips will let you know about situations where you should control depth of field.
When you photograph a landscape, everything in the frame / picture must be sharp and clear. And this applies to photographing city-spaces as well. For a maximum sharpness from foreground till the horizon in the background use a short focal length and an aperture around f/16 or smaller if required. Set your focus at about 1/3rd of the way in your scene. If you are shooting with a long exposure, use a tripod to keep your camera still and steady. And if you do not have a steady surface to keep your camera still, increase your ISO by one stop.
For any kind of portrait photography, to be successful, take shots where the background is beyond the depth of field and are consequently blurred. To shoot portraits you should use a combination of longer focal length and a wide aperture. Good portraits are those that stand out because the subject is sharp, clearly in focus while the background is blur or out of focus. TO get this result you need to control depth of field
Close up shots are meant to show details of a subject. Like for example if you are taking a close-up shot of a flower, it would be to see details of the petals or the pollen grains. To attract viewers to see what you want them to see, you should control depth of field to make sure all the attention is limited to the focused area and not everything that is there in the picture. So, when you photograph miniature subjects / object the choice of aperture becomes crucial.