What is Depth of Field ? The depth of field refers to which part of the image you want to appear in focus from foreground through to background and is determined by a combination of the aperture setting and the focal length of the lens.the aperture setting the focal length of the lens
The widest aperture (smallest f-number) gives the least or shallow depth of field. These images generally have a single object sharply focused, with the rest of the image blurry. This is a great and easy way to direct the viewer's attention.