How to Change the Depth of Field in Photographs
One aspect of focus — depth of field — is controlled in part by the aperture setting. Depth of field refers to how much of an image is in sharp focus. The larger the depth of field, the greater the zone of sharp focus.
In this figure, which has an aperture setting of f/3.4, only objects very close to the front mum are sharply focused — in other words, the picture has a short depth of field.
Reducing the aperture increases the depth of field, bringing more surrounding flowers into focus in this figure.
If your digital camera doesn’t offer aperture control or a zoom lens, you can use your photo editor’s blur filters to create the effect of a short depth of field in an existing picture.